Bilateral cisternal abducens nerve involvement with ophthalmoplegic migraine

To the Editor,

We read with great interest the recent article by Takizawa et al. in which they report atypical oculomotor nerve enhancement in ophthalmoplegic migraine in the orbit and cavernous sinus (1).

We recently evaluated a 36-year old woman with recurrent, self-limiting episodes of left frontal throbbing headaches accompanied by nausea and ophthalmoparesis, which occurred 5–6 times a year over the last three years. Her headaches responded to analgesics and resolved in 3–4 days. Certain odors trigger her attacks. She was on topiramate for headache prophylaxis and metoprolol for blood pressure control.

During this hospitalization, she presented to the Emergency department with left frontal headache, nausea and diplopia that had started two weeks earlier. Family history was significant for migraine in her mother. Examination revealed restricted left eye abduction on horizontal gaze. Her visual acuity was 20/20 in both eyes. Pupillary and fundoscopic exam were unremarkable. The remainder of her neurological exam was normal. Two days later, she developed mild restriction on right eye abduction.

A post contrast brain Magnetic Resonance Imaging (MRI) scan (Figure 1) showed bilateral abducens nerve enhancement in the cisternal portion. Magnetic Resonance Angiography (MRA) and Magnetic Resonance Venography (MRV) did not reveal any other intracranial pathology. A spinal tap demonstrated opening pressure of 27 cm water and closing pressure of 15 cm water. Antinuclear antibody, ANCA, ds DNA, IgG index, VZV, HSV, co GM1 triad, Lyme screen and western blot, TSH, vitamin B1, hemoglobin A1c, paraneoplastic panel were all within normal range. The presence of nausea and photophobia as migrainous features, the limited cranial nerve involvement and the lack of abnormal soft tissue enhancement in the ipsilateral cavernous sinus made Tolosa Hunt syndrome unlikely. Her headache and nausea improved on intravenous ketorolac. Gabapentin 600 mg three times a day was added to topiramate as prophylactic therapy. Since she was already on metoprolol for hypertension, we opted to use gabapentin. An examination performed two months later revealed normal extraocular movements.

Figure 1.

From top: (1) T2 weighted image showing cranial nerves. (2) Axial T1 weighted pre contrast image with no enhancements of cranial nerves. (3) Axial T1 weighted post contrast right sixth cranial nerve enhancement. (4) Axial T1 weighted curvilinear enhancement of the left sixth cranial nerve cisternal portion.

Ophthalmoplegic migraine or recurrent painful ophthalmoplegic neuropathy (PRON) is a rare, reversible disorder characterized by recurrent episodes of headaches accompanied or followed by unilateral ophthalmoplegia. There have been several case reports in the literature demonstrating involvement of the cisternal portion of the cranial nerves, more commonly involving the oculomotor nerve (1) and rarely the abducens nerve (2,3).

Most third nerve palsies are attributed to the trigeminovascular migraine epiphenomenon, which describes an activation of the trigeminal-vascular system to cause release of neuropeptides causing sterile inflammation of the oculomotor nerve, leading to ophthalmoplegia due to demyelination (4). This is due to the oculomotor nerve anatomy and porous blood-nerve barrier at its emergence from the brainstem (4).

So far there has been one case report describing cisternal abducens nerve enhancement by Lavin et al. (3). The pathogenesis of this enhancement is not well understood. The thin caliber of the abducens nerve makes its detection on MRI imaging difficult. Such cases require 3D reconstruction imaging to define the nerve and possible gadolinium uptake.

This is the first report of bilateral cisternal sixth cranial nerve enhancement in an adult patient with ophthalmoplegic migraine. As more advanced imaging becomes available, it is expected we will have more evidence of sixth cranial nerve involvement and better understanding of the pathogenesis involved.