Cranial Nerve Palsies
Certain systemic diseases are implicated in the aetiology of cranial nerve palsies. These are:
- Diabetes mellitus
- Tuberculosis
- Carcinoma
- Rheumatoid arthritis
- Systemic lupus erythaematosus (SLE) and other connective tissue disorders
- Sarcoidosis
- Leprosy
- Lyme disease
- HIV
- Amyloidosis
ALL of these can involve one or more cranial nerves. Guillain-Barre syndrome (GBS) and hereditary motor and sensory neuropathies (HMSN) are also associated with cranial nerve involvement. Cranial nerve palsies are well described in Listeria meningitis.
Cranial nerve palsy mimics
Certain other conditions masquerade as cranial nerve palsies. In particular:
- Myasthenia gravis causes weakness of the ocular muscles, and therefore mimics an ocular palsy
- Rabies can mimic GBS, including facial weakness
- Thyroid eye disease also causes a non-neurological ocular palsies
(see learning session on Cranial Nerves One to Six)
Unless there is an obvious cause, investigation for cranial nerve injury starts with imaging, either CT head or preferably MRI, if available. Imaging is mandatory for cranial nerve palsies associated with trauma.