Bilateral abducens palsies and facial weakness as initial manifestations of a Chiari 1 malformation

Chiari I malformations are rare, congenital anomalies involving the caudal herniation of the cerebellar tonsils into the upper cervical spinal canal. Osseous abnormalities of the skull permit the extension of the hindbrain below the foramen magnum and engender syringohydromyelia formation. Neuroophthalmic manifestations are not uncommon; nevertheless, this is the first report of concomitant bilateral abducens palsies and facial nerve impairment as presenting manifestations of a Chiari I malformation.

A 30-year-old black female presented with a recent history of blurred vision and binocular diplopia in both left and right gazes. Headaches, dizziness, and orofacial sensorimotor impairments were noted in conjunction with the onset of her diplopia. No history of surgery, trauma, or systemic illness was elicited. Extraocular motility testing confirmed a complete bilateral abduction deficit. Additional cranial nerve testing revealed bilateral facial nerve weakness and tactile hypesthesia in the perioral region. No taste disturbances were reported. Nuclear magnetic resonance imaging studies revealed a Chiari I malformation with a syringohydromyelia formation in the vicinity of the patient's sixth cervical vertebrae. Foramen magnum decompression surgery was performed. Two months after surgery, abduction capacity was restored along with resolution of symptoms of perioral numbness and signs of facial weakness.

Bilateral sixth nerve palsies are rare clinical commodities especially when they do not occur in isolation. Intracranial neoplams, trauma, subarachnoid hemorrhaging, demyelinating disease, and meningeal infarcts have all been shown to induce mixed cranial neuropathies. The concomitant bilateral abducens palsy and concomitant facial nerve weakness reported in this case represents an atypical and previously unreported presentation of a Chiari I malformation.