5.4. Cranial Nerve IV
- Anatomy
- Nucleus is below that of the IIIrd nerve at the level of the inferior colliculus
- Supplies the contralateral superior oblique muscle
- Longest intracranial course; emerges from the dorsal surface of the midbrain below the inferior colliculus and curses below the tentorium; enters the cavernous sinus below the IIIrd nerve, enters the orbit through the superior orbital fissure outside of the annulus of Zinn
- Blood supply:
- Anastomosis of ascending and descending branches of nutrient subpial arteries
- Superior cerebellar artery branches supply the IVth nerve nuclei
- Superior division of the intermediolateral trunk of the external carotid artery supplies the nerve in the superior orbital fissure
- Posterior lateral choroidal branch of PCA (p4)
- Vascular lesions (parenchymal):
- Nuclear IV as part of a superior cerebellar artery stroke
- Masugi's syndrome in which the IIIrd and IVth nerve are infarcted simultaneously; superior cerebellar artery; ipsilateral ataxia and contralateral loss of pain and temperature sensation below the clavicle
- May be involved in isolation; posterolateral choroidal artery from p4; associated pulvinar involvement
Congenital Defects
- Unilateral or bilateral absence of IV in association with absence of III, VI and other brainstem nuclei
Trauma
- 5% of cranial nerve palsies that follow severe head trauma afflict the IVth nerve
- Approximately 15% of all ocular palsies have traumatic origin; most compression or contusion injuries heal within 2–5 weeks
- Approximately 30% of IV nerve palsy are traumatic; brainstem is compressed against the lateral edge of the tentorium may damage both IVth nerves
- Orbital fractures may damage the IVth nerve
- Surgery involving the tentorium; anterior temporal lobectomy; top of basilar artery aneurysm surgery
- Post traumatic intracavernous aneurysm
External Carotid Artery Ischemia
- Involving the ILL of the external carotid artery or its superior branch (during course of embolization of vascular lesions or tumor)
- Diabetic induced infarction
- Arteritis
Systemic Disease
- Cavernous sinus infection and tumor (simultaneous involvement of III, VI, VI)
- Superior orbital fissure syndrome (tumor of the orbit or infection)
- Collagen vascular disease with infarction
- Diabetes
- Wegener's and necrotizing arteritides
Neuromuscular Junction Disease
- Congenital and acquired MG
- Tetanus
- Botulinum poisoning
- Neurotoxic snake venom
- Lambert–Eaton syndrome
Ocular Muscle Disease
- PEO
- Kearns-Sayre Syndrome
- Thyroid ophthalmopathy
- Orbital pseudotumor
Superior Oblique Myokymia
- Rapid spontaneous firing of the superior oblique muscle
- Congential superior oblique palsy
Neoplasms
- Tumors that invade the cavernous sinus: pituitary adenoma, meningioma, lymphoma
- Nasopharyngeal cancer
- Isolated neurinoma or Schwannoma
- Carcinoma of the sphenoid sinus
Infections
- Herpes zoster (rare); less common than III
- EBV; St. Louis, Eastern and Western equine viral infection
- Syphilis
- Lyme's
- HIV
- Purulent bacterial infections (meningeal involvement)
- Rare involvement with polio
- Mucormycosis
Immune Mediated
- Miller Fisher Syndrome
- CIDP
- Descending GBS
- MS (rare)
- Sarcoid (rare)
|