text:
## Journals

### Global optimization of spin Hamiltonians with gain-dissipative systems. (arXiv:1807.00699v1 [cs.ET])

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

Recently, several platforms were proposed and demonstrated a proof-of-principle for finding the global minimum of the spin Hamiltonians such as the Ising and XY models using gain-dissipative quantum and classical systems. The implementation of dynamical adjustment of the gain and coupling strengths has been established as a vital feedback mechanism for analog Hamiltonian physical systems that aim to simulate spin Hamiltonians. Based on the principle of operation of such simulators we develop a novel class of gain-dissipative algorithms for global optimisation of NP-hard problems and show its performance in comparison with the classical global optimisation algorithms. These systems can be used to study the ground state and statistical properties of spin systems and as a direct benchmark for the performance testing of the gain-dissipative physical simulators. The estimates of the time operation of the physical implementation of the gain-dissipative simulators for large matrices show a possible speed-up of the several orders of magnitude in comparison with classical computations.

Categories: Journals, Physics

### Quantum description of timing-jitter for single photon ON/OFF detectors. (arXiv:1807.00722v1 [quant-ph])

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

In the context of ultra-fast quantum communication and random number generation, detection timing-jitters represent a strong limitation as they can introduce major time-tagging errors and affect the quality of time-correlated photon counting or quantum state engineering. Despite their importance in emerging photonic quantum technologies, no detector model including such effects has been developed so far. We propose here an operational theoretical model based on POVM density formalism able to explicitly quantify the effect of timing-jitter for a typical class of single photon detector. We apply our model to some common experimental situations.

Categories: Journals, Physics

### Conditional channel simulation. (arXiv:1807.00784v1 [quant-ph])

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

In this work we design a specific simulation tool for quantum channels which is based on the use of a control system. This allows us to simulate an average quantum channel which is expressed in terms of an ensemble of channels, even when these channel-components are not jointly teleportation-covariant. This design is also extended to asymptotic simulations, continuous ensembles, and memory channels. As an application, we derive relative-entropy-of-entanglement upper bounds for private communication over various channels, from the amplitude damping channel to non-Gaussian mixtures of bosonic lossy channels. Among other results, we also establish the two-way quantum and private capacity of the so-called dephrasure' channel.

Categories: Journals, Physics

### Exact quantization of superconducting circuits. (arXiv:1807.00792v1 [cond-mat.mes-hall])

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

We present a theoretical description for circuits consisting of weak anharmonic qubits coupled to cavity multimodes. We obtain a unitary transformation that diagonalizes harmonic sector of the circuit. Weak anharmonicity does not alter the normal mode basis, however it can modify energy levels. We study two examples of a transmon and two transmons coupled to bus resonator, and we determine dressed frequencies and Kerr nonlinearities in closed form formulas. Our results are valid for arbitrary frequency detuning and coupling within and beyond dispersive regime.

Categories: Journals, Physics

### Classifying Data with Local Hamiltonians. (arXiv:1807.00804v1 [quant-ph])

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

The goal of this work is to define a notion of a quantum neural network to classify data, which exploits the low energy spectrum of a local Hamiltonian. As a concrete application, we build a binary classifier, train it on some actual data and then test its performance on a simple classification task. More specifically, we use Microsoft's quantum simulator, Liquid, to construct local Hamiltonians that can encode trained classifier functions in their ground space, and which can be probed by measuring the overlap with test states corresponding to the data to be classified. To obtain such a classifier Hamiltonian, we further propose a training scheme based on quantum annealing which is completely closed-off to the environment and which does not depend on external measurements until the very end, avoiding unnecessary decoherence during the annealing procedure. For a network of size n, the trained network can be stored as a list of O(n) coupling strengths. We address the question of which interactions are most suitable for a given classification task, and develop a qubit-saving optimization for the training procedure on a simulated annealing device. Furthermore, a small neural network to classify colors into red vs. blue is trained and tested, and benchmarked against the annealing parameters.

Categories: Journals, Physics

### Alternating, private alternating, and quantum alternating realtime automata. (arXiv:1407.0334v2 [cs.FL] UPDATED)

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

We present new results on realtime alternating, private alternating, and quantum alternating automaton models. Firstly, we show that the emptiness problem for alternating one-counter automata on unary alphabets is undecidable. Then, we present two equivalent definitions of realtime private alternating finite automata (PAFAs). We show that the emptiness problem is undecidable for PAFAs. Furthermore, PAFAs can recognize some nonregular unary languages, including the unary squares language, which seems to be difficult even for some classical counter automata with two-way input. Regarding quantum finite automata (QFAs), we show that the emptiness problem is undecidable both for universal QFAs on general alphabets, and for alternating QFAs with two alternations on unary alphabets. On the other hand, the same problem is decidable for nondeterministic QFAs on general alphabets. We also show that the unary squares language is recognized by alternating QFAs with two alternations.

Categories: Journals, Physics

### Family of Bell-like inequalities as device-independent witnesses for entanglement depth. (arXiv:1411.7385v2 [quant-ph] UPDATED)

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

We present a simple family of Bell inequalities applicable to a scenario involving arbitrarily many parties, each of which performs two binary-outcome measurements. We show that these inequalities are members of the complete set of full-correlation Bell inequalities discovered by Werner-Wolf-Zukowski-Brukner. For scenarios involving a small number of parties, we further verify that these inequalities are facet-defining for the convex set of Bell-local correlations. Moreover, we show that the amount of quantum violation of these inequalities naturally manifests the extent to which the underlying system is genuinely many-body entangled. In other words, our Bell inequalities, when supplemented with the appropriate quantum bounds, naturally serve as device-independent witnesses for entanglement depth, allowing one to certify genuine k-partite entanglement in an arbitrary $n\ge k$-partite scenario without relying on any assumption about the measurements being performed, nor the dimension of the underlying physical system. A brief comparison is made between our witnesses and those based on some other Bell inequalities, as well as the quantum Fisher information. A family of witnesses for genuine k-partite nonlocality applicable to an arbitrary $n\ge k$-partite scenario based on our Bell inequalities is also presented.

Categories: Journals, Physics

### On the derivation of the Hartree equation in the mean field limit: Uniformity in the Planck constant. (arXiv:1606.06436v6 [math.AP] UPDATED)

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

In this paper the Hartree equation is derived from the $N$-body Schr\''odinger equation in the mean-field limit, with convergence rate estimates that are uniform in the Planck constant $\hbar$. Specifically, we consider the two following cases:(a) T\''oplitz initial data and Lipschitz interaction forces, and (b) analytic initial data and interaction potential, over short time intervals independent of $\hbar$. The convergence rates in these two cases are $1/\sqrt{\log\log N}$ and $1/N$ respectively. The treatment of the second case is entirely self-contained and all the constants appearing in the final estimate are explicit. It provides a derivation of the Vlasov equation from the $N$-body classical dynamics using BBGKY hierarchies instead of empirical measures.

Categories: Journals, Physics

### Entanglement is necessary for emergent classicality in all physical theories. (arXiv:1705.08028v3 [quant-ph] UPDATED)

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

One of the most striking features of quantum theory is the existence of entangled states, responsible for Einstein's so called "spooky action at a distance". These states emerge from the mathematical formalism of quantum theory, but to date we do not have a clear idea of the physical principles that give rise to entanglement. Why does nature have entangled states? Would any theory superseding classical theory have entangled states, or is quantum theory special? One important feature of quantum theory is that it has a classical limit, recovering classical theory through the process of decoherence. We show that any theory with a classical limit must contain entangled states, thus establishing entanglement as an inevitable feature of any theory superseding classical theory.

Categories: Journals, Physics

### Rewiring Stabilizer Codes. (arXiv:1707.09403v2 [quant-ph] UPDATED)

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

We present an algorithm for manipulating quantum information via a sequence of projective measurements. We frame this manipulation in the language of stabilizer codes: a quantum computation approach in which errors are prevented and corrected in part by repeatedly measuring redundant degrees of freedom. We show how to construct a set of projective measurements which will map between two arbitrary stabilizer codes. We show that this process preserves all quantum information. It can be used to implement Clifford gates, braid extrinsic defects, or move between codes in which different operations are natural.

Categories: Journals, Physics

### Negation of photon loss provided by negative weak value. (arXiv:1707.09640v2 [quant-ph] UPDATED)

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

We propose a usage of a weak value for a quantum processing between preselection and postselection. While the weak value of a projector of 1 provides a process with certainty like the probability of 1, the weak value of -1 negates the process completely. Their mutually opposite effect is approved without a conventional weak' condition. In addition the quantum process is not limited to be unitary; in particular we consider a loss of photons and experimentally demonstrate the negation of the photon loss by using the negative weak value of -1 against the positive weak value of 1.

Categories: Journals, Physics

### On the size of chaos in the mean field dynamics. (arXiv:1708.07701v5 [math.AP] UPDATED)

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

We consider the error arising from the approximation of an N-particle dynamics with its description in terms of a one-particle kinetic equation. We estimate the distance between the j-marginal of the system and the factorized state, obtained in a mean field limit as N $\rightarrow$ $\infty$. Our analysis relies on the evolution equation for the "correlation error" rather than on the usual BBGKY hierarchy. The rate of convergence is shown to be O(j 2 N) in any bounded interval of time (size of chaos), as expected from heuristic arguments. Our formalism applies to an abstract hierarchical mean field model with bounded collision operator and a large class of initial data, covering (a) stochastic jump processes converging to the homogeneous Boltzmann and the Povzner equation and (b) quantum systems giving rise to the Hartree equation.

Categories: Journals, Physics

### Analytic model of thermalization: Quantum emulation of classical cellular automata. (arXiv:1709.06315v3 [cond-mat.stat-mech] UPDATED)

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

We introduce a novel method of quantum emulation of a classical reversible cellular automaton. By applying this method to a chaotic cellular automaton, the obtained quantum many-body system thermalizes while all the energy eigenstates and eigenvalues are solvable. These explicit solutions allow us to verify the validity of some scenarios of thermalization to this system. We find that two leading scenarios, the eigenstate thermalization hypothesis scenario and the large effective dimension scenario, do not explain thermalization in this model.

Categories: Journals, Physics

### Quantum fluctuation theorems for arbitrary environments: adiabatic and non-adiabatic entropy production. (arXiv:1710.00054v2 [quant-ph] UPDATED)

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

We analyze the production of entropy along non-equilibrium processes in quantum systems coupled to generic environments. First, we show that the entropy production due to final measurements and the loss of correlations obeys a fluctuation theorem in detailed and integral forms. Second, we discuss the decomposition of the entropy production into two positive contributions, adiabatic and non-adiabatic, based on the existence of invariant states of the local dynamics. Fluctuation theorems for both contributions hold only for evolutions verifying a specific condition of quantum origin. We illustrate our results with three relevant examples of quantum thermodynamic processes far from equilibrium.

Categories: Journals, Physics

### Learning hard quantum distributions with variational autoencoders. (arXiv:1710.00725v2 [quant-ph] UPDATED)

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

Studying general quantum many-body systems is one of the major challenges in modern physics because it requires an amount of computational resources that scales exponentially with the size of the system.Simulating the evolution of a state, or even storing its description, rapidly becomes intractable for exact classical algorithms. Recently, machine learning techniques, in the form of restricted Boltzmann machines, have been proposed as a way to efficiently represent certain quantum states with applications in state tomography and ground state estimation. Here, we introduce a new representation of states based on variational autoencoders. Variational autoencoders are a type of generative model in the form of a neural network. We probe the power of this representation by encoding probability distributions associated with states from different classes. Our simulations show that deep networks give a better representation for states that are hard to sample from, while providing no benefit for random states. This suggests that the probability distributions associated to hard quantum states might have a compositional structure that can be exploited by layered neural networks. Specifically, we consider the learnability of a class of quantum states introduced by Fefferman and Umans. Such states are provably hard to sample for classical computers, but not for quantum ones, under plausible computational complexity assumptions. The good level of compression achieved for hard states suggests these methods can be suitable for characterising states of the size expected in first generation quantum hardware.

Categories: Journals, Physics

### Optimising Matrix Product State Simulations of Shor's Algorithm. (arXiv:1712.07311v3 [quant-ph] UPDATED)

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

We detail techniques to optimise high-level classical simulations of Shor's quantum factoring algorithm. Chief among these is to examine the entangling properties of the circuit and to effectively map it across the one-dimensional structure of a matrix product state. Compared to previous approaches whose space requirements depend on $r$, the solution to the underlying order-finding problem of Shor's algorithm, our approach depends on its factors. We performed a matrix product state simulation of a 60-qubit instance of Shor's algorithm that would otherwise be infeasible to complete without an optimised entanglement mapping.

Categories: Journals, Physics

### Many-Body Spectral Reflection Symmetry and Protected Infinite-Temperature Degeneracy. (arXiv:1801.03101v2 [cond-mat.str-el] UPDATED)

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

Protected zero modes in quantum physics traditionally arise in the context of ground states of many-body Hamiltonians. Here we study the case where zero modes exist in the center of a reflection-symmetric many-body spectrum, giving rise to the notion of a protected "infinite-temperature" degeneracy. For a certain class of nonintegrable spin chains, we show that the number of zero modes is determined by a chiral index that grows exponentially with system size. We propose a dynamical protocol, feasible in ongoing experiments in Rydberg atom quantum simulators, to detect these many-body zero modes and their protecting spectral reflection symmetry. Finally, we consider whether the zero energy states obey the eigenstate thermalization hypothesis, as is expected of states in the middle of the many-body spectrum. We find intriguing differences in their eigenstate properties relative to those of nearby nonzero-energy eigenstates at finite system sizes.

Categories: Journals, Physics

### Population transfer at exceptional points in spectra of the hydrogen atom in parallel electric and magnetic fields. (arXiv:1802.01443v2 [quant-ph] UPDATED)

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

We study the population transfer between resonance states for a time-dependent loop around exceptional points in spectra of the hydrogen atom in parallel electric and magnetic fields. Exceptional points are well-suited for population transfer mechanisms, since a closed loop around these in parameter space commutes eigenstates. We address the question how shape and duration of the dynamical parameter loop affects the transferred population, in order to optimize the latter. Since the full quantum dynamics of the expansion coefficients is time-consuming, we furthermore present an approximation method, based on a $2\times 2$ matrix.

Categories: Journals, Physics

### The minimum error probability of quantum illumination. (arXiv:1802.02158v3 [quant-ph] UPDATED)

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

Quantum illumination is a technique for detecting the presence of a target in a noisy environment by means of a quantum probe. We prove that the two-mode squeezed vacuum state is the optimal probe for quantum illumination in the scenario of asymmetric discrimination, where the goal is to minimize the decay rate of the probability of a false positive with a given probability of a false negative. Quantum illumination with two-mode squeezed vacuum states offers a 6 dB advantage in the error probability exponent compared to illumination with coherent states. Whether more advanced quantum illumination strategies may offer further improvements had been a longstanding open question. Our fundamental result proves that nothing can be gained by considering more exotic quantum states, such as e.g. multi-mode entangled states. Our proof is based on a new fundamental entropic inequality for the noisy quantum Gaussian attenuators. We also prove that without access to a quantum memory, the optimal probes for quantum illumination are the coherent states.

Categories: Journals, Physics

### Quantum purification spectroscopy. (arXiv:1802.04638v2 [quant-ph] UPDATED)

arXiv.org: Quantum Physics - Tue, 2018-07-03 19:03

We discuss a protocol based on quenching a purified quantum system that allows to capture bulk spectral features. It uses an infinite temperature initial state and an interferometric strategy to access the Loschmidt amplitude, from which the spectral features are retrieved via Fourier transform, providing coarse-grained approximation at finite times. It involves techniques available in current experimental setups for quantum simulation, at least for small systems. We illustrate possible applications in testing the eigenstate thermalization hypothesis and the physics of many-body localization.

Categories: Journals, Physics


text:
1. Nov 3, 2014

### sergiokapone

If in the bottom of the bucket with water we made a hole, then water flows out of it. Bucket with water is the system with $m(t)$, thus we have to use equation:
$m(t)\frac{dv}{dt} = F + u\frac{dm}{dt}$.
Where $u\frac{dm}{dt}$ -- is jet reaction force.
But, I think the jet reaction force should not appear in this case. What is the solution of this paradox?

Last edited: Nov 3, 2014
2. Nov 3, 2014

### Danger

Hi, Sergio. If I understand the question correctly, there are two answers. A hole in the actually bottom would not provide thrust because the water would just be accelerating toward the ground as opposed to away from the bucket. That would lessen the effect of gravity upon the bucket because of weight loss, but that's not really a jet effect. If, on the other hand, the hole is in the side of the bucket near the bottom, there would be a tiny one because it would be pushing off from the water still in the container. I honestly think that I'm not correct in my interpretation of what you're asking though. Can you perhaps rephrase it?

3. Nov 3, 2014

### Staff: Mentor

I don't understand the question.

4. Nov 3, 2014

### sergiokapone

I do not completely understand this. How I can write the equation of motion in the case the bucket, which is on the floor?

5. Nov 3, 2014

### Danger

No help here... I don't know any math. I can say that there will be no motion at all if the thing is on the floor. (Unless you count immeasurably small structural vibrations on the molecular scale.) In fact, the water will just stop flowing completely if the surfaces of the bucket rim and the floor are smooth enough to form a seal.

Last edited: Nov 3, 2014
6. Nov 3, 2014

### sergiokapone

It is strange to me, the in the case of the rocket the outgoing propellant create jet forse, but in the case of bucket - whater is not.

7. Nov 3, 2014

### Danger

In the case of a rocket or air-breathing jet, or water jet or any other kind, the reaction mass is accelerated away from the container by either being expanded or being compressed and then released, or having the reaction chamber reduce in size to eject it (like in a syringe or balloon). In the bucket instance, gravity is simply pulling the water away from it. Earth is providing the force, not something in the bucket.

8. Nov 3, 2014

### A.T.

This is how a rocket produces thrust:

Where is the green force in the case of your bucket?

9. Nov 3, 2014

### sergiokapone

Ok, I understand that.

But now the quastion in the math. Why should I use equation of the motion $m(t)\frac{dv}{dt}=F$ instead $m(t)\frac{dv}{dt}=F + u\frac{dm}{dt}$? Is the $u$ -equal zero in this case? But, obviously it is not.

10. Nov 3, 2014

### A.T.

Define your symbols. What is F, v, m, u ?

11. Nov 3, 2014

### Danger

As mentioned, I don't know any math at all beyond simple geometry. What is "u"? If it's physical displacement on an x, y, or z axis, it is zero.

12. Nov 3, 2014

### sergiokapone

$u$ - is the propellant relative velocity (relative to rocket or some other thing, bucket, for example e.t.c.)

13. Nov 3, 2014

### A.T.

Velocity of what and when? What are the other symbols representing?

14. Nov 3, 2014

### sergiokapone

$u$ - is the propellant relative velocity
$F$ - external force, gravity force, for example
$v$ - is the velocity of the rocket
$m$ - is the current mass of the rocket

15. Nov 3, 2014

### Danger

Okay, but I rather suspect that the equation should apply only if there is some physical interaction between the two objects. In this case, there isn't. That would be like using it to determine the force between an aeroplane and canoe. What applies in your case is the gravity formula and how the bucket becomes lighter as water leaves it.

edit: You guys are posting too quickly for me to keep up with. I'm going to take a bathroom/TV break (it's the only room with a flatscreen) and I'll check in later.

Last edited: Nov 3, 2014
16. Nov 3, 2014

### sergiokapone

17. Nov 3, 2014

### A.T.

Okay, that should work for you bucket too.
Why not? If you make the hole to the side, it will create thrust an propel the bucket horizontally.

18. Nov 3, 2014

### sergiokapone

This is not interesting trivial case.
What if I will create the hole in the bottom?

19. Nov 3, 2014

### A.T.

Different direction of thrust.

20. Nov 3, 2014

format: plain


text:
Article Text

Olfactory groove meningioma with a 10-year history of smell loss and olfactory recovery after surgery
1. Andreas Steenholt Niklassen1,2,
2. Rasmus Langelund Jørgensen3 and
1. 1Flavour Institute, Department of Clinical Medicine, Aarhus Universitet, Aarhus C, Denmark
2. 2Department of Ear, nose and throat, Regional Hospital West, Holstebro, Denmark
3. 3Department of Neurosurgery, Aarhus University Hospital, Aarhus N, Denmark
1. Correspondence to Dr Andreas Steenholt Niklassen; an{at}clin.au.dk

## Abstract

A rare cause of olfactory impairment is olfactory groove meningiomas with insidious onset of non-specific symptoms like headache, olfactory dysfunction, psychiatric symptoms such as depression, personality changes, declining cognitive function, visual disturbances or seizures. A common complication of surgery is loss of olfactory function. Still, the preservation of olfactory function should be attempted as olfactory loss often has a severe negative impact on quality of life. This report describes a woman with an olfactory groove meningioma and a 10-year history of olfactory impairment. It includes preoperatively and postoperatively extended olfactory testing, a neurosurgical approach to preserve the olfactory function and postoperative olfactory rehabilitation. After rehabilitation, the patient regained a normal olfactory function, even though the right-sided olfactory nerve could not be preserved during surgery. The case demonstrates the importance of performing neuroimaging in selected patients with olfactory loss and a method for preserving and potentially improving postoperative olfactory function.

• ear
• nose and throat/otolaryngology
• neuroimaging
• neurooncology
• CNS cancer
• neurosurgery

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

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## Background

Clinical knowledge of how and when to refer patients with olfactory impairment to further investigations is paramount. A rare cause of olfactory impairment is olfactory groove meningiomas (OGM)—representing 5%–18% of intracranial meningiomas.1 The prevalence of pathologically confirmed meningiomas in the USA is 97.5/100 000, with an incidence rate of 8.36 for females and 3.61 for males out of 100 000 person-years.2 OGMs are benign, slow-growing tumours with usually insidious onset of non-specific symptoms like headache, olfactory dysfunction, psychiatric symptoms such as depression, personality changes, declining cognitive function, visual disturbances or seizures.1 3 4

A common complication of surgery for OGMs is loss of residual or severely impaired olfactory function . However, the preservation of olfactory function should be attempted5 as olfactory loss has a severe negative impact on quality of life.6

This report describes the management of a woman with an OGM and a 10-year history of olfactory impairment. The report includes preoperatively and postoperatively extended olfactory testing with evaluation in a specialised smell and taste clinic, a neurosurgical approach to preserve the olfactory function and postoperative olfactory rehabilitation.

Furthermore, the case demonstrates the importance of performing neuroimaging in selected patients with olfactory loss and a method for preserving and potentially improving postoperative olfactory function in OGM induced olfactory loss.

## Case presentation

The case presents a fit-and-well 56-year-old woman with a 10-year history of gradually decreasing olfactory function. The patient had 1.5 years previously been diagnosed with stress, and as a result, reduced her work capacity from full time to part time. This stress particularly influenced the patient’s ability for complex processing of tasks at hand, and the patient had to take one subtask at a time. During the previous 6 months, the patient had suffered from intermittent headaches but no history of nausea or vomiting. Our case begins as the patient was admitted to the emergency department with a first-time generalised seizure. Objective examination, including neurological examination, was normal, except for slight suspicion of dysarthria, which resolved.

## Investigations

On admission to the emergency department, an acute CT scan followed by a gadolinium-enhanced cerebral MRI was performed. These scans revealed an extra-axial mass on the anterior skull base with extension to the right frontal lobe, with homogeneous contrast uptake and significant perilesional oedema (see figure 1). The largest diameter of the mass was 30 mm (see figure 2). A multidisciplinary team conference was conducted with attendings from the neurosurgical, oncological, neurological and neuroradiological departments. Radiologically, the most likely diagnosis was an OGM, and the patient was referred to the neurosurgical department for assessment and treatment. As the tumour was symptomatic with perilesional oedema, informed consent for surgery was obtained. Before the scheduled surgery, the patient was referred to the Flavour smell and taste clinic for preoperative and postoperative examination of the olfactory function. The olfactory function was preoperatively tested with the extended version of the Sniffin’ Sticks7 (Burghart Messtechnik, Wedel, Germany) with a threshold score (T) of 2, discrimination score (D) of 7 and identification score (I) of 11. A total TDI score of 20—indicating severe hyposmia. No other causes of olfactory dysfunction were found.

Figure 1

Axial T2-weighted MRI showing the tumour and peritumoural oedema.

Figure 2

Sagittal gadolinium-enhanced T1-weighted MRI showing the size and classic location of OGM. OGM, olfactory groove meningioma.

## Treatment

### Pharmacological

The patient presented with generalised seizures, and antiepileptic medication with lamotrigine was prescribed. Due to increasing headaches and radiologically confirmed substantial white matter changes suggesting oedema, she was supplemented with oral steroids before surgery.

### Surgical

Based on the primarily right-sided basofrontal location, the absence of paranasal sinus infiltration and that the patient had intact but diminished olfactory function, a right-sided pterional craniotomy was performed to salvage the olfactory apparatus. Perioperatively, the right olfactory tract was found stretched around the basolateral side of the tumour and could not be preserved. The left olfactory tract was left intact. The tumour was completely resected, and the dural attachment coagulated, corresponding to a Simpson grade II resection.

## Outcome and follow-up

The immediate postoperative course was uneventful. However, on postoperative day 2, the patient had a generalised tonic-clonic seizure. The postoperative generalised seizure was abolished with intravenous diazepam and an increased dose of prophylactic lamotrigine with no further seizures. An acute CT scan showed expected postoperative changes with minimal blood in the tumour bed. The patient was discharged from the hospital on day three. Histological examination confirmed a benign meningioma. Follow-up contrast MRIs 3 and 12 months postoperatively were without evidence of recurrence, and the oedema had subsided.

Due to complaints of reduced short-term memory and concentration difficulties, the patient was referred for neuropsychological testing and referred to further neurocognitive rehabilitation. Despite rehabilitation, the patient still suffered from reduced working memory and problems handling more complex tasks one year after surgery. Consequently, the patient was not yet able to return to her part-time job.

At the flavour clinic, follow-up was performed 12 months after surgery, where the olfactory function was retested with the extended Sniffin’ Sticks test.7 The TDI score had improved to 33 (an improvement from 20), with a threshold score of 4, a discrimination score of 14 and an identification score of 15. This reflects a normal olfactory function—a significant improvement from the presurgical olfactory function.

## Discussion

Olfactory impairment is prevalent in 15% of the general population.8 Most patients are diagnosed with an underlying aetiology, but up to 23% remain with no apparent cause and are subsequently classified as idiopathic.9 Typically, these patients are referred for further investigations with MRI to rule out potentially treatable intracranial disease. However, the hit rate of MRI revealing an underlying treatable central cause of olfactory dysfunction in idiopathic anosmics/hyposmics is as low as 0.08%, according to Rudmik et al.10 Hoekman et al investigated 130 cases of idiopathic olfactory loss, and only one finding of multiple sclerosis (0.8%) was potentially the cause of olfactory dysfunction.11 Decker et al investigated 122 cases of idiopathic smell loss and found 31 cases of causal findings for dysosmia. Most of these were due to sinusitis, but two cases of olfactory meningioma were found (1.6%).12

This calls for debate whether MRI should be standard practice in idiopathic olfactory loss or be reserved for cases with a higher clinical risk of intracranial disease. A recent study examined a modelling-based economic evaluation of routine MRI for idiopathic olfactory loss. It found that while MRI (US$2400) had a 100% sensitivity in diagnosing intracranial tumours, the no-imaging strategy (US$86) had a 98% sensitivity.10 The incremental cost per diagnosis for the MRI strategy compared with the no-imaging strategy was US\$115 669.50. They conclude the most cost-effective strategy is not to perform routine MRI in these patients and that it could be cost-effective in cases when the a priori clinical probability of treatable intracranial disease reaching 7.9%.10

Our case describes the importance of correct diagnostics and treatment for olfactory meningioma and potential good outcome with preservation—and even improvement—of the olfactory function. In the present case, the improvement in olfactory function can most likely be prescribed to reduced oedema on the left side following resection of the right-sided tumour. Preoperatively, the right-sided olfactory function was impaired by the tumour and the left-sided olfactory function by significant oedema. During surgery, the right-sided nerve was not preserved due to tumour growth and had to be removed. This completely removed the right-side olfactory function postoperatively. After surgery, the oedema diminished, and the left-sided nerve regained normal function. To find the needle in the haystack, it is paramount to identify which symptoms warrant an MRI scan. The most frequent presenting symptoms include mono-symptomatic headache, personality changes, olfactory dysfunction or visual impairment.13

In the current case, olfactory dysfunction was present for 10 years, headaches for 6 months and disabling psychiatric stress-related symptoms for 18 months before diagnosis. Using the suggested MRI strategy, the patient should have been correctly diagnosed sooner, which may have reduced the load of cognitive difficulties after surgery. However, further studies are needed to investigate this diagnostic pipeline.

Olfactory dysfunction ranging from hyposmia to complete anosmia is an early symptom of OGMs and found in 58.5%–71.7% of patients with OGMs.,4 5 14 but only 6.4%–15% of patients have olfactory dysfunction as their presenting symptom.1 4 5 Extended olfactory testing is not routinely performed in patients with OGMs, and olfactory outcomes following surgery are variably tested and reported.1 5 15–17 The surgical treatment carries a high risk, up to 89.7%, of decreased or complete loss of olfactory.1 However, as the olfactory function is only rarely tested preoperatively and postoperatively, the true incidence of preoperative dysfunction is unknown, and the complication rate of deteriorating olfactory function likely under-reported.

Numerous reports suggest that the risk depends on the surgical approach, with unilateral approaches are more likely to preserve preoperative olfactory function.5 18 Besides a higher risk of postoperative anosmia, the classic bilateral subfrontal approach has higher morbidity and mortality than unilateral approaches.4 14 16 Besides the classic transcranial approaches within the last decade, endoscopic endonasal resection of OGM’s through the cribriform plate has been explored as a minimally invasive procedure to reduce surgical morbidity. Even though this technique seems to be advantageous with regards to visual outcome when it comes to olfactory function, this technique carries a higher risk of anosmia as well as postoperative cerebrospinal fluid leak increasing the risk of postoperative meningitis and the need for reoperation.19 20

Gerber et al report on a patient with a large OGM with preoperative anosmia treated with a bifrontal craniotomy and careful dissection of the olfactory tracts. At follow-up, after 15 months, the patient had regained her sense of smell.21 Also, Bassiouni et al report improving olfactory function in two (4,9%) patients following surgery.4

Our case encourages the use of the pterional approach for OGMs. By preserving the contralateral olfactory tract, preoperative hyposmia can even improve following complete tumour removal. Furthermore, it underlines the need for more studies with thorough preoperative and postoperative olfactory testing to fully uncover the extent of olfactory dysfunction due to OGMs and the potential to improve this overseen neurological deficit by choosing the correct surgical approach. In cases where the laterality of remaining olfactory function is uncertain based on neuroimaging, unilateral olfactory testing on both sides can be advantageous.

### Patient’s perspective

About 10 years ago, I started noticing my sense of smell was deteriorating gradually, but, at the moment, I thought it was just an average age decline. About 1.5 years before discovering the meningioma, I was diagnosed with stress, which happened after an episode where I couldn’t even find my own home, and someone else had to walk me home. I was on sick leave for 6 months and was in a terrible condition during that time. I started working again but couldn’t handle my job full time, so I worked part-time after that. From the stress diagnosis and until discovering the meningioma, I still had ups and downs. I remember many headaches and had to stay in bed for several days at different times during that period. One night, I went into generalised seizures, where my husband found me, and I was brought into the emergency department at the hospital, where I had a scan that discovered the meningioma. Two months went by before I was scheduled for surgery. Before surgery, I had a preoperative status of the function of my smell, which accounted to severely reduced sense of smell.

I had the surgery done in December 2019, and I was really in a terrible condition the following month; and I think If I had been 20 years older, I wouldn’t have made it. At least not mentally—maybe physically. I tried getting back to work, which had been my plan, and I started part-time with 4–6 hours a week gradually increasing, but I just couldn’t handle it anymore. Primarily because of the fatigue, but maybe also my lack of ability to have an overview of things. Secondarily, I had memory issues, concentration issues, and difficulties speaking and understanding spoken words when I was tired or fatigued. Furthermore, I was often confused and dizzy. I was used to having lots of things going on simultaneously, working as a department manager, but I just couldn’t anymore. Nothing worked; I couldn’t read—it just didn’t stay with me. And I was tired all the time. My concentration and memory were terrible. It still is. I was referred to neurorehabilitation at a centre, where I stayed for 3 months, which was terrific, and I learnt many strategies to cope. I feel much better now, even though I had to go on early retirement and stopped working. I still have to sleep during the day to make it through the day. Focusing on my sense of smell, it has definitely improved after the surgery, as it was almost completely gone presurgery. I think the smell training helped me improve, but I stopped doing it eventually. Everyone in the healthcare system helped me, and I am so grateful for the people who cared for me during the most challenging period of my life.

### Learning points

• In patients with olfactory loss and concomitant headache, personality change or visual impairment, MRI should always be performed.

• When choosing the correct surgical strategy, olfactory function can be preserved—and potentially improved—following surgery in olfactory groove meningioma (OGM) patients.

• A multidisciplinary approach for presurgical and postsurgical treatment of OGM is recommended to improve overall outcome and quality of life.


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Introduction
Default values
7. INSERT using DEFAULT for all columns
Summary

## Instruction

Amazing! What about using DEFAULT for all columns? You can use a statement like this:

INSERT INTO all_defaults_table VALUES (DEFAULT, DEFAULT, DEFAULT, DEFAULT, DEFAULT);

SQL again allows you to use a shorter query:

INSERT INTO all_defaults_table DEFAULT VALUES;

Using DEFAULT for every table column is a very rare case, so we don't need to discuss it in detail. Just remember that you can use this syntax if needed.

## Exercise

Click to continue.