A supranuclear gaze palsy is an inability to look in a particular direction as a result of cerebral impairment. There is a loss of the voluntary aspect of eye movements, but, as the brainstem is still intact, all the reflex conjugate eye movements are normal.
The type of gaze problem is dependent upon the lesion - thus a right hemisphere lesion, particularly the frontal lobes, leads to a contralateral gaze palsy, i.e. an inability to look away from the lesion.
More obscure examples are seen in conditions like progressive supranuclear palsy and Parkinson's disease, where there is a vertical gaze palsy.
The clinical features that distinguish a vertical gaze palsy from third, fourth or sixth nerve palsies include:
In a vertical gaze palsy:
- both eyes are affected
- pupils are often unequal but fixed
- generally there is no diplopia
- the reflex eye movements, e.g. on extending or flexing the neck - are intact