Results of extraocular muscle surgery for superior oblique myokymia

Segmental Imaging of the Trochlear Nerve: Anatomic and Pathologic Considerations

BACKGROUND

The trochlear nerve (the fourth cranial nerve) is the only cranial nerve that arises from the dorsal aspect of the midbrain. The nerve has a lengthy course making it highly susceptible to injury. It is also the smallest cranial nerve and is often difficult to identify on neuroimaging.

EVIDENCE ACQUISITION

High-resolution 3-dimensional skull base MRI allows for submillimeter isotropic acquisition and is optimal for cranial nerve evaluation. In this text, the detailed anatomy of the fourth cranial nerve applicable to imaging will be reviewed.

RESULTS

Detailed anatomic knowledge of each segment of the trochlear nerve is necessary in patients with trochlear nerve palsy. A systematic approach to identification and assessment of each trochlear nerve segment is essential. Pathologic cases are provided for each segment.

CONCLUSIONS

A segmental approach to high-resolution 3-dimensional MRI for the study of the trochlear nerve is suggested.

Superior oblique myokymia, a review

PURPOSE OR REVIEW

Superior oblique myokymia is a rare, monocular condition that typically presents in healthy adults. In this article, we review the proposed pathophysiology, describe the typical clinical presentation, and discuss the recommended work up and various treatment options.

RECENT FINDINGS

Treatment for this condition ranges from observation and reassurance to various topical and systemic medications. Both strabismus surgery and neurosurgery are reserved for patients who fail medical therapy or are intolerant to medication secondary to side effects.

SUMMARY

Due to its episodic nature, SOM is often under-diagnosed. We highlight key features in a patient's clinical history and the examination findings that suggest and support the diagnosis, with review of available treatment options.

Recurrent Superior Oblique Myokymia Treated by Distal Tendon Extirpation

BACKGROUND

We describe successful surgical treatment of superior oblique myokymia, which had recurred after superior oblique tenectomy.

METHODS

Single case report.

RESULTS

The distal stump of the superior oblique tendon was extirpated by stripping it from the globe. The ipsilateral superior rectus muscle also was recessed, to correct a hypertropia that had resulted from the original superior oblique tenectomy.

CONCLUSIONS

Complete removal of the distal superior oblique muscle tendon provided definitive relief of superior oblique myokymia. Superior rectus muscle recession, combined with previous inferior oblique myectomy, compensated effectively for loss of superior oblique function.

Superior Oblique Myokymia: Some Novel Observations

Superior oblique myokymia is a rare condition, characterized by spontaneous rhythmic contractions of the superior oblique muscle and was first described by Duane in 1906. However, the pathophysiology of this condition remains poorly understood even today. A number of medical and surgical treatment modalities have been tried, with variable results. We report a case of superior oblique myokymia in a pregnant female, which could be triggered with flashlight stimulation, and the result of treatment with timolol maleate 0.5% ophthalmic solution.

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

OPINION STATEMENT

Neurovascular compression syndromes are characterized by recurrent attacks of neurological symptoms and clinical signs depending on the cranial nerve affected. It is assumed that pulsatile compression of the nerve is caused mainly by an artery. The result is segmental demyelination of the transition zone or the central part of the cranial nerve, which is covered by oligodendrocytes, and subsequent ephaptic axonal transmission. Compression of the vestibular nerve can cause attacks of spinning or non-spinning vertigo: vestibular paroxysmia. Compression of the trochlear nerve is characterized by attacks of monocular oscillopsia: superior oblique myokymia. Damage to ocular motor nerves due to local radiation or rarely neurovascular compression can also lead to oscillopsia and double vision precipitated by sustained excentric gaze: ocular neuromyotonia. It is important to note that controlled trials have so far not been performed for any of these three syndromes, mainly because of their low prevalence. Therefore, treatment recommendations are based on single cases or small case series and thus have the lowest level of evidence. The sodium channel blockers carbamazepine (50 to 200 mg tid) or oxcarbazepine (100 to 300 mg tid) are evidently effective in most of the patients who have these three syndromes. However, one should always keep in mind the contraindications, side effects, and interactions with other drugs of carbamazepine ( http://www.nlm.nih.gov/medlineplus/druginfo/meds/a682237.html ) All patients require regular laboratory examinations. Alternatives are other sodium channel blockers such as phenytoin (100 to 300 mg tid), gabapentin (100 to 600 mg tid), or valproic acid (100 to 300 mg tid). Furthermore, there are also few reports on the effects of beta blockers, which may be explained by their reduction of the amplitude of blood pressure. Patients who do not respond to pharmacotherapy require further diagnostics to determine the possibility of other etiologies. Some of these patients benefit from surgical decompression of the affected nerve.

Topical timolol in the treatment of monocular oscillopsia secondary to superior oblique myokymia: a review

Some reports have outlined many different treatment strategies for superior oblique myokymia (SOM) that attempt to reduce or eliminate patients' symptoms of monocular oscillopsia and/or diplopia. Most treatment strategies have focused solely on oral medications or invasive surgery. The following is a current and critical review of SOM along with its clinical findings/symptoms, demographics, theories of its pathogenesis, management/treatment options, new observations in SOM, as well as a case report to highlight a relatively novel idea for the treatment of SOM: topical timolol eye drops. It also highlights evidence of a new "localized theory" regarding topical β-blockers' mechanism of action in SOM compared to the previous systemic hypothesis proposed in 1994. The case report shows a 29-year-old female patient who suffered with SOM symptoms for 8-10 years and then experienced a worsening of her symptoms shortly postpartum. The patient was prescribed topical timolol eye drops by the author in the affected eye based on one case report(12) from 1994, which completely eliminated her symptoms within 1-2 days of starting the treatment with any recurrence with the daily use of the drop at the time of this article. Given the robust effect in this case, topical timolol may be a potentially useful drug in the management of SOM given its affordability and safer side effect profile in comparison to the oral medications traditionally used in SOM.