Cranial nerve enhancement on three-dimensional MRI in Miller Fisher syndrome

Miller Fisher syndrome (MFS) is characterized by an acute onset of external ophthalmoplegia, cerebellar ataxia, and areflexia. Because MFS is often preceded by an episode of acute inflammatory symptoms and, in most cases, the neurologic symptoms recover after a certain period of time, the disease is regarded as a variant of Guillain-Barre syndrome (GBS). ^[1] Although the involvement of peripheral nerves is evident in GBS, controversy still exists as to the localization of lesions in MFS. ^[2] Here we report two cases of MFS in which, using contrast-enhanced three-dimensional (3-D) MRI, the abducens and oculomotor nerves were enhanced by Gd-DTPA.

Patient 1.

The patient was a 26-year-old man with a history of transient diarrhea and sore throat 1 week before he complained of diplopia and unstable gait. On admission (the fifth day of illness), his external ocular movements were limited to all directions with the right abducens nerve being most severely affected. His gait was ataxic and his deep tendon reflexes were completely absent. ELISA ^[3] showed a high titer of IgG anti-GQ1b antibody (1:3,200) in the serum. CSF examination disclosed a mild elevation of protein concentration (65 mg/dL) without pleocytosis. He was treated with double filtration plasmapheresis and immunoabsorption after the ninth day of illness. His neurologic symptoms including diplopia and ataxia were gradually ameliorated from the 13th day and his deep tendon reflexes appeared around the 24th day.

On the 10th day when his ophthalmoplegia was most severe, contrast-enhanced 3-D MRI of the brain was performed, which was obtained by spoiled gradient-recalled acquisition in a steady state, using a 1.5-T system after injection of Gd-DTPA, ^[4] and it revealed a marked Gd-enhancement of the right abducens nerve (Figure 1, A and B) and a slight thickening of the right oculomotor nerve. Routine brain MRI did not show any abnormality on T_1- and T_2-weighted images. On the 101st day when his symptoms almost disappeared, the intensity of the enhancing nerves was markedly decreased (Figure 1, C).

• Download figure
• Open in new tab
• Download powerpoint

Figure 1. Contrast-enhanced 3-D MRI in Miller Fisher syndrome (A-C, patient 1; D, patient 2). Transverse (A and C) and sagittal (B and D) reformatted images through the right abducens nerve (A-C) and through the right oculomotor nerve (D) after gadolinium administration. A and B show a Gd-enhancement of the right abducens nerve (arrows), and D shows the enhancing right oculomotor nerve (arrow). The intensity of the right abducens nerve (A) is markedly decreased after symptomatic improvement (C).

Patient 2.

A 54-year-old man with a preceding history of cough and fever for 2 weeks showed progressive neurologic deficits, including diplopia, unstable gait, difficulty in writing, and then a decrease in visual acuity of both eyes. On admission the eighth day after onset), he had complete ophthalmoplegia, ataxia, and areflexia. His pupils were dilated and reactive sluggishly to light. CSF had an elevated protein concentration (72 mg/dL) without pleocytosis. With steroid treatment after the 11th day, his neurologic symptoms were ameliorated. By the 64th day, his cerebellar ataxia disappeared completely with only mild abducens palsy remaining.

On the ninth day, contrast-enhanced 3-D MRI of the brain was performed and it revealed a Gd-enhancement of the extramedullary portions of the oculomotor (Figure 1, D) and abducens nerves. No abnormality was detectable on conventional brain MRI.

Discussion.

The present two patients with MFS presented with an acute onset of external ophthalmoplegia, cerebellar ataxia, and areflexia preceded by an episode of acute inflammatory symptoms, and these neurologic signs improved or recovered. CSF examination showed a mild increase in protein concentration without pleocytosis. Although not examined in patient 2, patient 1 had anti-GQ1b antibody in the serum. In these cases, routine brain MRI did not show any abnormal findings, but contrastenhanced 3-D MRI revealed Gd-enhancement of the abducens nerves in patients 1 and 2 and of the oculomotor nerve in patient 2. Although not all affected nerves enhanced, these enhancing cranial nerves were functionally impaired most severely among the ocular nerves at the time of MRI examination. Because cranial nerves do not contrast-enhance in normal subjects, ^[5] the MRI findings represent involvement of the extramedullary portion of the oculomotor and abducens nerves in our cases of MFS.

Campylobacter jejuni isolated from MFS patients has a GQ1b epitope, and anti-GQ1b antibody may be found in the serum of MFS patients. ^[3,6,7] GQ1b is localized to the paranodal regions of the extramedullary portion of the oculomotor, trochlear, and abducens nerves. ^[7] Therefore, the anti-GQ1b antibody may attack the paranodes of these nerves, resulting in the induction of immunologic-inflammatory process. The present MRI findings may reflect it in the extramedullary portion of the abducens and oculomotor nerves.

In conclusion, the present observation provides direct evidence in living patients that the ophthalmoplegia in MFS results from peripheral lesions of the cranial nerves associated with ocular movements.