Therapy of Vestibular Paroxysmia, Superior Oblique Myokymia, and Ocular Neuromyotonia

[The six most frequent peripheral vestibular syndromes]

Three forms of peripheral vestibular disorders, each with its typical symptoms and clinical signs, can be differentiated functionally, anatomically and pathophysiologically: 1. inadequate unilateral paroxysmal stimulation or rarely inhibition of the peripheral vestibular system, e. g., BPPV, Menière's disease, vestibular paroxysmia or syndrome of the third mobile windows; 2. acute unilateral vestibulopathy leading to an acute vestibular tone imbalance manifesting as an acute peripheral vestibular syndrome; and 3. loss or impairment of function of the vestibular nerve and/or labyrinth: bilateral vestibulopathy. For all of these diseases, current diagnostic criteria by the Bárány-Society are available with a high clinical and scientific impact, also for clinical trials. The treatment depends on the underlying disease. It basically consists of 5 principles: 1. Explaining the symptoms and signs, pathophysiology, aetiology and treatment options to the patient; this is important for compliance, adherence and persistence. 2. Physical therapy: A) For BPPV specific liberatory maneuvers, depending on canal involved. Posterior canal: The new SémontPLUS maneuver is superior to the regular Sémont and Epley maneuvers; horizontal canal: the modified roll-maneuver; anterior canal the modified Yacovino-maneuver; 3. Symptomatic or causative drug therapy. There is still a deficit of placebo-controlled clinical trials so that the level of evidence for pharmacotherapy is most often low. 4. Surgery, mainly for the syndrome of the third mobile windows. 5. Psychotherapeutic measures for secondary functional dizziness.

Clinical Reasoning: A 73-Year-Old Woman With Episodic Dysarthria and Horizontal Binocular Diplopia

A 73-year-old woman presented with transient episodes of dysarthria and horizontal diplopia. She had stereotactic radiosurgery 18 years prior for a retroclival meningioma. Neurologic examination was notable for right-sided tongue deviation, tongue fasciculations, and intermittent impaired abduction of the right eye. MRI ruled out recurrence or progression of the retroclival meningioma. EEG failed to reveal electrographic seizures. EMG showed spontaneous depolarizations in bursts that sounded like "marching soldiers" in the right hemitongue, consistent with myokymia. Focal myokymia is an unusual EMG finding that is usually seen in demyelinating disorders, after radiation, or in neoplastic/inflammatory conditions. The clinical presentation and EMG findings were most consistent with delayed radiation-induced myokymia. Similar cases of transient dysarthria and tongue myokymia from radiation have been infrequently reported in the literature; however, this case uniquely exhibited additional episodes of transient horizontal diplopia, which was possibly from ocular myokymia or neuromyotonia. Although there are limited data, sodium channel inhibitors (e.g., carbamazepine, oxcarbazepine, and lacosamide) have shown some success to provide symptomatic relief, most likely secondary to their ability to inhibit underlying peripheral nerve hyperexcitability. Our patient was started on lacosamide 50 mg twice a day with a notable decrease in symptom frequency. This case illustrates the importance of detailed clinical and electrodiagnostic studies in making the diagnosis of delayed radiation-induced myokymia with episodic dysarthria and provides guidance on potential therapeutics.

Vestibular paroxysmia: Clinical features and imaging findings; a literature review

According to the definition of neurovascular compression syndromes (NVCS), a vascular structure in direct contact with a cranial nerve is causing mechanical irritation of the neural tissue producing correlating symptoms. Vestibular paroxysmia is an example of a neurovascular compression which is caused by neurovascular contact between the eighth cranial nerve and a vessel. It is crucial to understand the unique anatomy of the vestibulocochlear nerve in order to study the syndrome which is the result of its compression. More specifically, the long transitional zone between central and peripheral myelin plays a central role in clinical significance, as the transitional zone is the structure most prone to mechanical injury. Imaging techniques of the eighth cranial nerve and the surrounding structures are substantial for the demonstration of clinically significant cases and potential surgical decompression. The goal of the current review is to present and study the existing literature on vestibular paroxysmia and to search for the most appropriate imaging technique for the syndrome. An extensive literature search of PubMed database was performed, and the studies were ranked based on evidence-based criteria, followed by descriptive statistics of the data. The present analysis indicates that 3D CISS MRI sequence is superior to any other sequence, in the most studies reviewed, regarding the imaging of neurovascular compression of the eighth cranial nerve.

Ocular neuromyotonia caused by a recurrent sphenoidal ridge meningioma

Background

Ocular neuromyotonia (ONM) is a rare ocular motility disorder characterized by involuntary paroxysmal extraocular muscle contraction and is caused by radiation therapy, vascular compression, and inflammatory disease. This study includes a rare case of ONM caused by a recurrent meningioma.

Case Description

A 56-year-old man presented with diplopia due to the right oculomotor nerve palsy caused by a sphenoidal atypical meningioma, with improved symptoms after initial surgery. During the next 7 years, he underwent local radiation therapy, second surgery, and Gamma Knife radiosurgery to control the tumor's repetitive recurrence around the right anterior clinoid process. After these treatments, residual tumor was controlled for the next 3 years. However, 3 months after his last visit, he started to suffer from the right ONM and visual disturbance. The magnetic resonance imaging results revealed a rapid growth of the posterior part of the residual tumor, involving the right oculomotor nerve. The third tumor resection was performed to prevent further aggravation of the symptoms. Decompression of the right oculomotor nerve was achieved, and ONM disappeared immediately after surgery.

Conclusion

If nerve compression by the tumor is clearly indicated with the neuroradiological assessment, surgical intervention is the treatment of choice to improve ONM.

Superior Oblique Myokymia Presumed Due to Large Posterior Fossa Arteriovenous Malformation

A 26-year-old female presented with a complaint of intermittent oscillopsia and binocular vertical diplopia for the past 5 years. Over the past several months, she had noticed intermittent pulsatile tinnitus. She was otherwise healthy with no previous history of trauma and had no other visual or neurologic complaints. In Neuro-ophthalmology clinic, she was found to have 20/15 vision in both eyes with full ocular motility. There was a small exophoria in primary position and small esophoria in downgaze. Her slit lamp and fundus examinations were normal. During the assessment, the left eye was noted to undergo high-frequency, small amplitude incyclotorsional oscillations for a few seconds at a time (Video 1 in the supplementary material), which she was able to provoke by looking down. The diagnosis of superior oblique myokymia was made, and an MRI/MRA of the brain was requested.

Clinical long-term observation of the keyhole microvascular decompression with local anesthesia on diagnosis and treatment of vestibular paroxysmia

Background: The pathophysiology and etiology of vestibular paroxysmia (VP) remains unclear, moreover, due to the lack of reliable diagnostic features for VP, the clinical diagnosis will be made mainly by exclusion.Aims/objectives: To evaluate the diagnostic value and curative effect of keyhole microvascular decompression with local anesthesia for VP.Material and methods: 54 patients with trigeminal neuralgia, hemifacial spasm and glossopharyngeal neuralgia underwent keyhole microvascular decompression with local anesthesia, twelve of whom were coexistent with VP. The evaluation of the vertigo after operation was performed with symptom report card for 12 patients with VP and the mean follow-up period was 116 months (range 114-118 months).Results: The cochleovestibular neurovascular compression at the root zone of vestibular nerve was found in 12 patients with VP, of whom 11 patients had the neurovascular compressive vertigo induced intra-operatively and the vertigo disappeared postoperatively, moreover, one patient had no neurovascular compressive vertigo induced intra-operatively and the vertigo was not improved significantly after operation. Of 12 patients with VP during the mean 116-month follow-up, 11 patients had no recurrence of neurovascular compressive vertigo and the effective control rate of vertigo was 91.7%.Conclusions and significance: Keyhole microvascular decompression with local anesthesia is not only an effective method for treating VP and controlling neurovascular compressive vertigo, but also has definite clinical significance in the diagnosis of VP.

Superior Oblique Myokymia: A Case Report of Surgical Treatment, Review of the Literature, and Consideration of Surgical Approach

BACKGROUND

Superior oblique myokymia (SOM) is a rare disorder characterized by episodic microtremor of the eyeball. in patients with SOM, intermittent contraction of the superior oblique muscle causes irregular and rotatory eye movement, causing oscillopsia and diplopia. Microvascular decompression (MVD) of the trochlear nerve is potentially a definitive treatment method for SOM; however, owing to its rarity, this disorder is not well-known to neurosurgeons, and thus the optimal surgical approach has not yet been determined.

CASE DESCRIPTION

A 77-year-old woman with left SOM had experienced oscillopsia for 2 years. MVD was performed via a left lateral superior cerebellar approach with the patient in the park-bench position. Her symptom resolved immediately after the surgery.

CONCLUSIONS

We believe that MVD via a left lateral superior cerebellar approach can be safely performed to SOM in elderly patients like our patient. Therefore, MVD should be considered as the definitive treatment method for more patients with SOM.

Congenital Ocular Neuromyotonia with Partial Third Nerve Palsy

PURPOSE

We report the first case of congenital ocular neuromyotonia (ONM) and the results of strabismus surgery for this patient's co-existing cranial nerve (CN) III palsy.

PATIENTS AND METHOD

The patient presented at 18 months with strabismus that had reportedly been present since the time of birth. On exam, she had persistent exotropia (RXT) and hypertropia (RHT) with episodes of esotropia in the right eye that could be evoked by sustained left gaze. A diagnosis of ONM with partial CN III palsy was made. T1-weighted, T2-weighted, and fluid-attenuated inversion recovery magnetic resonance imaging failed to reveal intracranial pathology.

RESULTS

Gaze induced intermittent esotropia resolved with carbamazepine. Surgery was performed to improve the patient's RXT and RHT. Post-operatively, the patient's RXT had improved from 12 to 15 prism diopters (∆) at near and 20∆ at a distance to 10∆ RXT at near with no horizontal deviation at distance. Her deviation has remained stable for 13 years, as has her neurological exam and good state of health.

CONCLUSION

This case demonstrates that ONM may present congenitally and adds to the body of knowledge regarding surgical outcomes on concurrent CN palsies in these patients.

Ocular neuromyotonia

Ocular neuromyotonia is a rare, albeit treatable, ocular motor disorder, characterised by recurrent brief episodes of diplopia due to tonic extraocular muscle contraction. Ephaptic transmission in a chronically damaged ocular motor nerve is the possible underlying mechanism. It usually improves with carbamazepine. A 53-year-old woman presented with a 4-month history of recurrent episodes of binocular vertical diplopia (up to 40/day), either spontaneously or after sustained downward gaze. Between episodes she had a mild left fourth nerve palsy. Sustained downward gaze consistently triggered downward left eye tonic deviation, lasting around 1 min. MR scan of the brain was normal. She improved on starting carbamazepine but developed a rash that necessitated stopping the drug. Switching to lacosamide controlled her symptoms.

Vestibular paroxysmia: Diagnostic criteria

This paper describes the diagnostic criteria for vestibular paroxysmia (VP) as defined by the Classification Committee of the Bárány Society. The diagnosis of VP is mainly based on the patient history and requires: A) at least ten attacks of spontaneous spinning or non-spinning vertigo; B) duration less than 1 minute; C) stereotyped phenomenology in a particular patient; D) response to a treatment with carbamazepine/oxcarbazepine; and F) not better accounted for by another diagnosis. Probable VP is defined as follows: A) at least five attacks of spinning or non-spinning vertigo; B) duration less than 5 minutes; C) spontaneous occurrence or provoked by certain head-movements; D) stereotyped phenomenology in a particular patient; E) not better accounted for by another diagnosis.

Ephaptic discharges in the proximal part of the 8th cranial nerve, which is covered by oligodendrocytes, are the assumed mechanism. Important differential diagnoses are Menière’s disease, vestibular migraine, benign paroxysmal positional vertigo, epileptic vestibular aura, paroxysmal brainstem attacks (in multiple sclerosis or after brainstem stroke), superior canal dehiscence syndrome, perilymph fistula, transient ischemic attacks and panic attacks. Current areas of uncertainty in the diagnosis of VP are: a) MRI findings of vascular compression which are not diagnostic of the disease or predictive for the affected side because they are also observed in about 30% of healthy asymptomatic subjects; and b) response to treatment with carbamazepine/oxcarbazepine supports the diagnosis but there are so far no randomized controlled trials for treatment of VP.

A randomized double-blind, placebo-controlled, cross-over trial (Vestparoxy) of the treatment of vestibular paroxysmia with oxcarbazepine

Objective

Vestibular paroxysmia (VP) is characterized by short, often oligosymptomatic attacks of vertigo which occur spontaneously or are sometimes provoked by turning the head. Despite the description of the disease almost 40 years ago (first termed “disabling positional vertigo”), no controlled treatment trial has been published to date. The Vestparoxy trial was designed as a randomized, placebo-controlled, double-blind cross-over trial to examine the therapeutic effect of oxcarbazepine (OXA) in patients with definite or probable VP.

Methods

Patients were recruited from August 2005 to December 2011 in the outpatient Dizziness Unit of the Department of Neurology of the Munich University Hospital, and randomized to receive OXA (first week: 300 mg once per day, second week: 300 mg b.i.d., third week: 300 mg t.i.d. until the end of the third month), followed by placebo or vice versa with a 1-month wash-out period in between. The primary endpoint was the number of days with one or more attacks. Secondary endpoints were the number of attacks during the observed days, and the median (for each day) duration of attacks. All these endpoints were assessed using standardized diaries collected at the end of each treatment phase.

Results

Forty-three patients were randomized, 18 patients provided usable data (2525 patient days) for at least one treatment phase and were included in the main (intention-to-treat) analysis. The most common reasons for discontinuation documented were adverse events. The risk of experiencing a day with at least one attack was 0.41 under OXA, and 0.62 under placebo treatment, yielding a relative risk of 0.67 (95% CI 0.47–0.95, p = 0.025). The number of attacks during the observed days ratio was 0.53 (95% CI 0.42–0.68, p < 0.001) under OXA compared to placebo. Median attack duration was 4 s (Q25: 2 s, Q75: 120 s) under OXA, and 3 s (Q25: 2 s, Q75: 60 s) under placebo treatment. When days with no attacks, i.e., duration = 0, were included in the analysis, these figures changed to 0 (Q25: 0, Q75: 3 s), and 2 (Q25: 0, Q75: 6 s). No serious adverse events or new safety findings were identified during the trial.

Conclusions

The Vestparoxy trial showed a significant reduction of VP attacks under OXA compared to placebo treatment, confirming the known and revealing no new side effects.