Microvascular decompression for superior oblique myokymia

Abstract

Superior oblique myokymia (SOM) is a rare eye movement disorder presenting as uniocular rotatory microtremor due to intermittent contractions of the superior oblique muscle. Medical treatment usually fails to provide long-term benefit for the patient and has considerable side effects. Surgical alternatives including tenotomy or partial tenectomy of the superior oblique tendon often result in incomplete resolution of the visual symptoms. The authors report a patient who experienced immediate cessation of disabling SOM following microvascular decompression of the fourth nerve at the root exit zone. Temporary double vision at downgaze resolved 5 months after surgery. There was no recurrence of oscillopsia during a follow-up of 22 months to date. From this single observation it appears likely that vascular compression of the trochlear nerve could be a significant pathophysiological factor contributing to SOM. In the hands of an experienced surgeon, microvascular decompression at the brainstem exit zone of this nerve may evolve as the method of choice for selected cases of disabling SOM.

Superior oblique myokymia: Efficacy of medical treatment

“…13 This theory has received support from ultrathin section MRI scanning 14 and from a report of successful treatment of SOM with microvascular decompression. 15 Patient 19, who subsequently developed hemifacial spasm ipsilateral to her SOM, is particularly interesting in this regard. Vascular compression is an established cause of hemifacial spasm 16 and the occurrence of the two entities in the same patient is an interesting association in favor of this mechanism.…”

Results of extraocular muscle surgery for superior oblique myokymia

“…2,14,20 Neurophysiological studies have suggested that SOM may result from defective supranuclear input to the trochlear nucleus, with secondary regeneration of motor neurons. 11,12,14,[21][22][23] In 1983 Bringewald 24 first postulated that SOM could result from vascular compression of the trochlear nerve and others have subsequently confirmed this hypothesis. [25][26] Since none of the patients in our series had magnetic resonance imaging performed in the manner necessary to document this finding, we cannot comment on whether any of our patients had neurovascular compression.…”

“…3 Many patients have spontaneous relapses and remissions over years and symptoms can be exacerbated by stress, caffeine, or nicotine. 3 Treatment options for patients with SOM are both medical 4-10 and surgical, 2,3,5,7,[11][12][13][14][15][16][17][18][19] with surgery being recommended only after medical treatment has failed. Although neurovascular decompression of the trochlear nerve has been reported as a treatment for SOM, [11][12][13] most reports of surgical management describe extraocular muscle surgery in the form of weakening the ipsilateral superior oblique and inferior oblique.…”

Microvascular Compression of the Vestibulocochlear Nerve

“…2 Other clinical syndromes such as spasmodic torticollis [15], cyclic oculomotor spasm with paresis [16], superior oblique myokymia [17,18], and abducens spasm [19] may also be initiated by vascular compressions of the respective cranial nerves (nerves intermedius, spinal accessory nerve, and oculomotor and trochlear nerves). The incidence of the different MVC syndromes seems to be related to the length of the central nervous system (CNS) segment [20].…”