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A 35 year old man suddenly developed the inability to move his eyes to the right. He has been entirely healthy, taking no medications, and lacking any family history of neurologic disorders. You find that his eyes have normal sight, appear structurally normal, but do not move beyond mid position to the right, even with the doll’s eye (“oculocephalic”) maneuver. There are no other neurologic abnormalities. For example, vertical eye movements are completely normal.
Where is the lesion?
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Correct!
This patient has a palsy of right horizontal conjugate gaze (“gaze palsy”) that involves saccades, pursuit, and the vestibulo-ocular reflex. Although
you could postulate lesions affecting muscles or the neuromuscular junction that are activated in right gaze, such a symmetrical deficit of conjugate
gaze to one side will virtually always originate within the brain. If volitional and reflex gaze are both completely impaired, expect to find the
lesion in the pons.
Are you surprised that there are no other neurologic deficits, like seventh nerve palsy, internuclear ophthalmoplegia, nystagmus, ataxia, or limb weakness? You are right that lesions here usually cause such deficits. But if the lesion is confined to a small area in the tegmental pons—in the location of the sixth nerve nucleus--you might not find any such accompanying signs (although you should look for them as “fellow travelers”).
This patient had a hemorrhage from a right pontine tegmental cavernous malformation (“cavernoma”).
The only effective treatment is surgical excision, which is hazardous.
No treatment was undertaken here. The deficits gradually resolved enough to give him partial restoration of right gaze. He was advised to avoid any activity that would generate increased intracranial pressure, like weight-lifting, evacuative straining, and standing on his head.
Are you surprised that there are no other neurologic deficits, like seventh nerve palsy, internuclear ophthalmoplegia, nystagmus, ataxia, or limb weakness? You are right that lesions here usually cause such deficits. But if the lesion is confined to a small area in the tegmental pons—in the location of the sixth nerve nucleus--you might not find any such accompanying signs (although you should look for them as “fellow travelers”).
This patient had a hemorrhage from a right pontine tegmental cavernous malformation (“cavernoma”).
No treatment was undertaken here. The deficits gradually resolved enough to give him partial restoration of right gaze. He was advised to avoid any activity that would generate increased intracranial pressure, like weight-lifting, evacuative straining, and standing on his head.
Incorrect