Trochlear Nerve Palsy (Cranial IV palsy)


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:

MRI brain with and without contrast
TFT, fasting glucose, ESR
CSF: meningitis
Tests for head and neck cancer: transneural spread


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


  • Idiopathic
  • Vasculopathy:
    • Atheroma, Hypertension, Diabetes mellitus
    • Giant cell arteritis
  • Trauma

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