Sixth Nerve Palsy Flashcards
A sixth cranial nerve palsy refers to dysfunction of the … nerve that causes a lateral rectus palsy.
A sixth cranial nerve palsy refers to dysfunction of the abducens nerve that causes a lateral rectus palsy.
A sixth cranial nerve palsy refers to dysfunction of the abducens nerve that causes a lateral rectus palsy.
The abducens nerve is the sixth (VI) cranial nerve, which provides innervation to the lateral rectus muscle. This is one of the extra-ocular muscles that causes eye abduction, which is needed for horizontal gaze.
A VI nerve palsy is the most common cranial nerve palsy in isolation. A palsy can develop due to a lesion anywhere along the path of the nerve from pons to lateral rectus muscle.
The abducens nerve innervates the lateral … muscle.
The abducens nerve innervates the lateral rectus muscle.
Increases in intracranial pressure may result in unilateral or bilateral … nerve palsies. This is because of the long intracranial course of the VI nerve, which is particularly prone to compression along the skull base.
Increases in intracranial pressure may result in unilateral or bilateral abducens nerve palsies. This is because of the long intracranial course of the VI nerve, which is particularly prone to compression along the skull base.
A sixth nerve palsy is characterised by failure in eye abduction leading to…
A sixth nerve palsy is characterised by failure in eye abduction leading to horizontal diplopia.
4 symptoms of sixth nerve palsy
Diplopia: worse on horizontal gaze in direction of lesion
Blurred vision
Dizziness
Eye pain
Signs in 6th nerve palsy
Failed eye abduction: ipsilateral to the lesion (unilateral or bilateral)
Strabismus: abnormal eye alignment. May only be present on lateral gaze initially
Accompanying features
These may be seen in patients with a nonisolated sixth nerve palsy.
V Brainstem signs (e.g. hemiparesis, hemisensory loss, dysarthria/dysphagia)
Raised ICP (e.g. headache, nausea, papilloedema)
Orbital signs: proptosis (eye protrusion), chemosis (conjunctival swelling), visual changes
Additional cranial nerve involvement: lesions of III, IV, VI, V1 may be seen in orbital apex syndrome or cavernous sinus pathology
Neuroimaging - 6th nerve palsy
This is the investigation of choice for a sixth nerve palsy. Magnetic resonance imaging (MRI) is the modality of choice, but a computed tomography (CT) of the head may be completed initially to exclude major differentials (e.g. tumour, intracerebral haemorrhage) whilst awaiting an MRI.
Neuroimaging is needed to exclude the majority of causes of a sixth nerve palsy. The urgency of imaging depends on the cause. In adults, a sixth nerve palsy is commonly isolated due to microvascular damage to the nerve (i.e. ischaemic mononeuropathy). In these cases, the need for urgent imaging of the head is less pressing.
The treatment of a sixth nerve palsy is directed towards the underlying cause.
There are numerous causes of a sixth nerve palsy and treatment should be directed towards the underlying cause. This is particularly relevant for infectious, inflammatory of neoplastic lesions, whereby treatment may alleviate diplopia.
In patients with an isolated, unilateral, nontraumatic sixth nerve palsy (usually due to microvascular disease), spontaneous recovery is common. This is also true for traumatic sixth nerve palsies.
In patients with persistent symptoms, or those unlikely to recover (e.g. bilateral at presentation or complete palsy), treatments can include patching (covering one eye to prevent binocular diplopia), use of prisms, strabismus surgery or even botox injections. Patients should be referred to an ophthalmologist.
