A 16 y.o. comes to the ED with trouble with his vision.
What is wrong?
Our patient had a 6th nerve palsy caused by compression of the nerve in the cavernous sinus. He had multiple lymph nodes in the scalp and biopsy showed large B cell lymphoma possibly Burkitt’s. On MRI the pt had enlargement of the pituitary gland due to lymphoma and diffuse marrow replacement with multiple areas of epidural soft tissue enlargement and organomegaly . There were bilateral 6th nerve palsies and a L 7th nerve palsy. He was started on rasbuicase and chemo with vincristine, cytoxan and dexamethasone. He has been improving.
infiltration of the cavernous sinus by lymphoma
There are six major syndromes of 6th nerve palsy. The course extends from the dorsal pons to the lateral rectus muscle. It can be mechanically compressed anywhere along its course and also can be affected by stroke, trauma, viral illness or just increased intracranial pressure.
the sixth nerve travels from the pons to the lateral rectus
SIX SYNDROMES of 6th nerve palsy
The course of the 6th nerve in relation to the cavernous sinus
1. The brainstem- involvement of the sixth nerve as it exits the brainstem often includes the 7th and 8th cranial nerve as well as the anterior pyramidal tracts. Tumors are often associated with this 6th nerve palsy.
2. Increased intracranial pressure- any lesion in the brain that causes increased ICP can cause a palsy of the sixth nerve because of its long course and pressure from brain swelling . This includes benign intracranial hypertension, subarachnoid hemorrhage, or tumors.
3. The petrous portion of the temporal bone- The sixth nerve can be affected here by complicated otitis media. Gradenigo’s syndrome refers to a constellation of sixth nerve palsy, same sided hearing loss, and same sided facial pain in the cranial nerve V distribution.
4. The cavernous sinus- The course of the sixth nerve through the cavernous sinus associates it with the 3rd, 4th and 5th cranial nerves. Lesions associated with sixth nerve palsy here are carotid cavernous fistulas, tumors and aneursyms of the carotid. Often proptosis is present. Tolosa-Hunt syndrome is a sterile inflammation that affects the anterior portion of the cavernous sinus.
5. Orbital syndrome of the sixth nerve- tumors of the orbit may cause proptosis and congestion of the conjunctival vessels or chemosis of the conjunctiva . This can occur in thyroid disease as well.
6. Isolated sixth nerve palsy syndromes- When no other cause is found; the “isolated sixth nerve palsy” is diagnosed. This is thought to be a vascular infarct occurring in diabetes, temporal arteritis or hypertension Sometimes it occurs after a viral infection or migraine.
THREE THINGS TO RULE OUT WHEN YOU SEE A 6th NERVE PALSY
Thyroid disease
An old orbital fracture( the medial rectus can become entrapped causing a 6th n. palsy)
Myasthenia gravis
Azarmina M, Azarmina H. The six syndromes of the sixth cranial nerve. J Ophthalmic Vis Res. 2013 Apr;8(2):160-171.
Robertson D, Hines J, Rucker C. Acquired sixth-nerve palsy in children. Arch Ophthalmol 1970;83:574-579.
Kline L, Bhatti M, Chung S. et al. Basic and clinical science course; Neuro-ophthalmology San Francisco: American Academy of Ophthalmology; 2010-2011.