Faculty Bibliography

Perception of the spatial vertical is important for maintaining and stabilizing vertical posture during body motion. The velocity storage pathway of vestibulo-ocular reflex (VOR), which integrates vestibular, optokinetic, and proprioception in the vestibular nuclei vestibular-only (VO) neurons, has spatio-temporal properties that are defined by eigenvalues and eigenvectors of its system matrix. The yaw, pitch and roll eigenvectors are normally aligned with the spatial vertical and corresponding head axes. Misalignment of the roll eigenvector with the head axes was hypothesized to be an important contributor to the oscillating vertigo during MdDS. Based on this, a treatment protocol was developed using simultaneous horizontal opto-kinetic stimulation and head roll (OKS-VOR). This protocol was not effective in alleviating the MdDS pulling sensations. A model was developed, which shows how maladaptation of the yaw eigenvector relative to the head yaw, either forward, back, or side down, could be responsible for the pulling sensation that subjects experience. The model predicted the sometimes counter-intuitive OKS directions that would be most effective in re-adapting the yaw eigenvector to alleviate the pulling sensation in MdDS. Model predictions were consistent with the treatment of 50 patients with a gravitational pulling sensation as the dominant feature. Overall, pulling symptoms in 72% of patients were immediately alleviated after the treatment and lasted for 3 years after the treatment in 58% of patients. The treatment also alleviated the pulling sensation in patients where pulling was not the dominant feature. Thus, the OKS method has a long-lasting effect comparable to that of OKS-VOR readaptation. The study elucidates how the spatio-temporal organization of velocity storage stabilizes upright posture and how maladaptation of the yaw eigenvector generates MdDS pulling sensations. Thus, this study introduces a new way to treat gravitational pull which could be used alone or in combination with previously proposed VOR readaptation techniques.

ABSTRACT/UNASSIGNED:A collection of instructional videos that illustrate a step by step approach to tele-neuro-ophthalmology and neuro-otology visits. These videos provide instruction for patient preparation for their video visit, patient and provider interface with an electronic medical record associated video platform, digital applications to assist with vision testing, and practical advice for detailed remote neuro-ophthalmologic and neuro-otologic examinations.

The virtual practice has made major advances in the way that we care for patients in the modern era. The culture of virtual practice, consulting, and telemedicine, which had started several years ago, took an accelerated leap as humankind was challenged by the novel coronavirus pandemic (COVID19). The social distancing measures and lockdowns imposed in many countries left medical care providers with limited options in evaluating ambulatory patients, pushing the rapid transition to assessments via virtual platforms. In this novel arena of medical practice, which may form new norms beyond the current pandemic crisis, we found it critical to define guidelines on the recommended practice in neurotology, including remote methods in examining the vestibular and eye movement function. The proposed remote examination methods aim to reliably diagnose acute and subacute diseases of the inner-ear, brainstem, and the cerebellum. A key aim was to triage patients into those requiring urgent emergency room assessment versus non-urgent but expedited outpatient management. Physicians who had expertise in managing patients with vestibular disorders were invited to participate in the taskforce. The focus was on two topics: (1) an adequate eye movement and vestibular examination strategy using virtual platforms and (2) a decision pathway providing guidance about which patient should seek urgent medical care and which patient should have non-urgent but expedited outpatient management.

Recurrent episodes of neurological dysfunction and white matter lesions in a young adult raise suspicion for multiple sclerosis (MS). However, occlusive retinopathy, hearing loss and absence of CSF oligoclonal bands are atypical for MS and should make the clinician consider an alternative diagnosis. We describe a man with hearing loss, visual signs and symptoms, and an accumulating burden of brain lesions, who was treated for a clinical diagnosis of MS for nearly two decades. Genetic testing revealed a unifying diagnosis.

We present diagnostic criteria for mal de débarquement syndrome (MdDS) for inclusion into the International Classification of Vestibular Disorders. The criteria include the following: 1] Non-spinning vertigo characterized by an oscillatory sensation ('rocking,' 'bobbing,' or 'swaying,') present continuously or for most of the day; 2] Onset occurs within 48 hours after the end of exposure to passive motion, 3] Symptoms temporarily reduce with exposure to passive motion (e.g. driving), and 4] Symptoms persist for >48 hours. MdDS may be designated as "in evolution," if symptoms are ongoing but the observation period has been less than 1 month; "transient," if symptoms resolve at or before 1 month and the observation period extends at least to the resolution point; or "persistent" if symptoms last for more than 1 month. Individuals with MdDS may develop co-existing symptoms of spatial disorientation, visual motion intolerance, fatigue, and exacerbation of headaches or anxiety. Features that distinguish MdDS from vestibular migraine, motion sickness, and persistent postural perceptual dizziness (PPPD) are reviewed. Motion-moderated oscillatory vertigo can also occur without a motion trigger, typically following another vestibular disorder, a medical illness, heightened psychological stress, or metabolic disturbance. Terminology for this non-motion triggered presentation has been varied as it has features of both MdDS and PPPD. Further research is needed into its phenomenological and biological relationship to MdDS, PPPD, and other vestibular disorders.

Although motion of the head and body has been suspected or known as the provocative cause for the production of motion sickness for centuries, it is only within the last 20 yr that the source of the signal generating motion sickness and its neural basis has been firmly established. Here, we briefly review the source of the conflicts that cause the body to generate the autonomic signs and symptoms that constitute motion sickness and provide a summary of the experimental data that have led to an understanding of how motion sickness is generated and can be controlled. Activity and structures that produce motion sickness include vestibular input through the semicircular canals, the otolith organs, and the velocity storage integrator in the vestibular nuclei. Velocity storage is produced through activity of vestibular-only (VO) neurons under control of neural structures in the nodulus of the vestibulo-cerebellum. Separate groups of nodular neurons sense orientation to gravity, roll/tilt, and translation, which provide strong inhibitory control of the VO neurons. Additionally, there are acetylcholinergic projections from the nodulus to the stomach, which along with other serotonergic inputs from the vestibular nuclei, could induce nausea and vomiting. Major inhibition is produced by the GABA_B receptors, which modulate and suppress activity in the velocity storage integrator. Ingestion of the GABA_B agonist baclofen causes suppression of motion sickness. Hopefully, a better understanding of the source of sensory conflict will lead to better ways to avoid and treat the autonomic signs and symptoms that constitute the syndrome.

BACKGROUND: Deep brain stimulation of the subthalamic nucleus (STN) has demonstrated efficacy in improving motor disability in Parkinson's disease. The recently developed quantitative susceptibility mapping (QSM) technique, which can accurately map iron deposits in deep brain nuclei, promises precise targeting of the STN. OBJECTIVE: To demonstrate the use of QSM to target STN effectively by correlating with classical physiological-based targeting measures in a prospective study. METHODS: The precision and accuracy of direct targeting with QSM was examined in a total of 25 Parkinson's disease patients between 2013 and 2015 at our institution. QSM was utilized as the primary magnetic resonance imaging (MRI) method to perform direct STN targeting on a stereotactic planning station utilizing computed tomography/MR fusion. Intraoperative microelectrode recordings (MER) were obtained to confirm appropriate trajectory through the sensorimotor STN. RESULTS: Estimations of STN thickness between the MER and QSM methods appeared to be correlated. Mean STN thickness was 5.3 mm. Kinesthetic responsive cells were found in > 90% of electrode runs. The mean radial error (+/-SEM) was 0.54 +/- 0.1 mm. Satisfactory clinical response as determined by Unified Parkinson's Disease Rating Scale (UPDRS III) was seen at 12 mo after surgery. CONCLUSION: Direct targeting of the sensorimotor STN using QSM demonstrates MER correlation and can be safely used for deep brain stimulation lead placement with satisfactory clinical response. These results imply that targeting based on QSM signaling alone is sufficient to obtain reliable and reproducible outcomes in the absence of physiological recordings.

The Mal de Debarquement syndrome (MdDS) generally follows sea voyages, but it can occur after turbulent flights or spontaneously. The primary features are objective or perceived continuous rocking, swaying, and/or bobbing at 0.2 Hz after sea voyages or 0.3 Hz after flights. The oscillations can continue for months or years and are immensely disturbing. Associated symptoms appear to be secondary to the incessant sensation of movement. We previously suggested that the illness can be attributed to maladaptation of the velocity storage integrator in the vestibular system, but the actual neural mechanisms driving the MdDS are unknown. Here, based on experiments in subhuman primates, we propose a series of postulates through which the MdDS is generated: (1) The MdDS is produced in the velocity storage integrator by activation of vestibular-only (VO) neurons on either side of the brainstem that are oscillating back and forth at 0.2 or 0.3 Hz. (2) The groups of VO neurons are driven by signals that originate in Purkinje cells in the cerebellar nodulus. (3) Prolonged exposure to roll, either on the sea or in the air, conditions the roll-related neurons in the nodulus. (4) The prolonged exposure causes a shift of the pitch orientation vector from its original position aligned with gravity to a position tilted in roll. (5) Successful treatment involves exposure to a full-field optokinetic stimulus rotating around the spatial vertical countering the direction of the vestibular imbalance. This is done while rolling the head at the frequency of the perceived rocking, swaying, or bobbing. We also note experiments that could be used to verify these postulates, as well as considering potential flaws in the logic. Important unanswered questions: (1) Why does the MdDS predominantly affect women? (2) What aspect of roll causes the prolongation of the tilted orientation vector, and why is it so prolonged in some individuals? (3) What produces the increase in symptoms of some patients when returning home after treatment, and how can this be avoided? We also posit that the same mechanisms underlie the less troublesome and shorter duration Mal de Debarquement.

The mal de debarquement syndrome (MdDS) is a movement disorder, occurring predominantly in women, is most often induced by passive transport on water or in the air (classic MdDS), or can occur spontaneously. MdDS likely originates in the vestibular system and is unfamiliar to many physicians. The first successful treatment was devised by Dai et al. (1), and over 330 MdDS patients have now been treated. Here, we report the outcomes of 141 patients (122 females and 19 males) treated 1 year or more ago. We examine the patient's rocking frequency, body drifting, and nystagmus. The patients are then treated according to these findings for 4-5 days. During treatment, patients' heads were rolled while watching a rotating full-field visual surround (1). Their symptom severity after the initial treatment and at the follow-up was assessed using a subjective 10-point scale. Objective measures, taken before and at the end of the week of treatment, included static posturography. Significant improvement was a reduction in symptom severity by more than 50%. Objective measures were not possible during the follow-up because of the wide geographic distribution of the patients. The treatment group consisted of 120 classic and 21 spontaneous MdDS patients. The initial rate of significant improvement after a week of treatment was 78% in classic and 48% in spontaneous patients. One year later, significant improvement was maintained in 52% of classic and 48% of spontaneous subjects. There was complete remission of symptoms in 27% (32) of classic and 19% (4) of spontaneous patients. Although about half of them did not achieve a 50% improvement, most reported fewer and milder symptoms than before. The success of the treatment was generally inversely correlated with the duration of the MdDS symptoms and with the patients' ages. Prolonged travel by air or car on the way home most likely contributed to the symptomatic reversion from the initial successful treatment. Our results indicate that early diagnosis and treatment can significantly improve results, and the prevention of symptomatic reversion will increase the long-term benefit in this disabling disorder.