Diagnosis:
This is a clinical diagnosis
Clinical features:
Rare in isolation
In neutral gaze: slight head tilted contralateral to the weak superior oblique muscle (loss of in-torsion)
Test with eye adducted and moved inferiorly. This is also the position of worse diplopia
If bilateral: on horizontal gaze, the abducting eye drifts downwards (inferior rectus of the contralateral eye overacts)
Investigations to consider:
CT
MRI brain with and without contrast
TFT, fasting glucose, ESR
CSF: meningitis
Tests for head and neck cancer: transneural spread
Treatment:
Treat underlying disease
Causes of trochlear nerve palsy (CN IV):
Nuclear & fasciular:
- Tumours: glioma, medulloblastoma
- Part of a Brainstem stroke syndrome
Basilar area:
- Meningitis:
- Bacterial, Meningovascular syphilis
- TB meningitis
- Fungal meningitis
- Basilar artery aneurysm
Cavernous sinus area:
- Internal Carotid artery aneurysm
- Cavernous sinus thrombosis
Superior orbital fissure & Orbital apex area:
- Tumours: nasopharygeal, meningioma, hemangioma, glioma, sarcoma, Hand-Schuller-Christian disease, metastasis
- AVMs
- Tolosa-Hunt syndrome
- Pseudotumour of the orbit
Others:
- Idiopathic
- Vasculopathy:
- Atheroma, Hypertension, Diabetes mellitus
- Giant cell arteritis
- Trauma