Disorders Nerve•Cranial6 SECTIONMotor Ocular Single

Third Cranial Nerve Palsy

Key Facts

•Damage to third cranial nerve causing reduced adduction, supraduction, infraduction, ptosis, and/or mydriasis with reduced constriction to light

•Common causes:

•reduced perfusion to intracranial segment of the nerve in diabetes or arteriosclerosis (ischemic palsy) • compression by intracranial aneurysm or other mass lesions • head trauma • meningitis

•Most urgent rule-out diagnosis: intracranial aneurysm

•Brain MRI/magnetic resonance angiography or CT/CT angiography, indicated in nearly all cases, will be negative in ischemic palsy but will usually detect an aneurysm

Clinical Findings

•Any combination of deficits in adduction, supraduction, infraduction, ptosis, and/ or mydriasis with reduced constriction to light

•No other manifestations need be present (isolated palsy)

Ancillary Testing

•MRI/magnetic resonance angiography or CT/CT angiography in all patients except when the evidence for an ischemic palsy is overwhelming, as in:

•older adult • arteriosclerotic risk factors • complete ductional deficits and ptosis • complete sparing of pupil • no history to suggest an underlying pertinent systemic disease

•When interpreted by an experienced radiologist, brain MRI and CT angiography are nearly 100% sensitive to brain aneurysm causing third cranial nerve palsy

•When suspicion for aneurysm is high and non-invasive imaging is negative, catheter cerebral angiography should be done

•If intracranial studies are negative, consider body imaging to rule out occult systemic inflammatory or neoplastic disorder

•If no recovery within 3 months, perform brain MRI

Differential Diagnosis

•Graves disease

•Orbital myositis

•Orbital tumor

•Traumatic orbitopathy

•Myasthenia gravis

•Fourth cranial nerve palsy

•Internuclear ophthalmoplegia

•Skew deviation

Treatment

•Extraocular muscle surgery if:

•palsy stable for ≥9 months

•some adduction, supraduction, and infraduction are present

•For patients who are not surgical candidates or who have failed extraocular muscle surgery, consider a monocular occluding (painted) contact lens if diplopia is troublesome

Prognosis

Fig. 6.1 Right third cranial nerve palsy. The right eye displays complete ptosis, a dilated pupil, and absent adduction, supraduction, and infraduction. The left eye is normal. This is a complete third cranial nerve palsy; incomplete forms, which are more common, may partially or completely spare the eyelid, the pupil, and some ocular ductions.

A

B

C

Fig. 6.2 Aneurysmal third cranial nerve palsy. (A) Cerebral angiogram shows aneurysm arising from internal carotid artery at its junction with the posterior communicating artery (arrow). Not shown is its compression of the third cranial nerve. (B) A three-dimensional reconstruction based on the angiogram also shows the aneurysm (arrow). (C) After coiling, the aneurysm no longer fills with contrast dye (arrow).

Palsy Nerve Cranial Third

Disorders Nerve•Cranial6 SECTIONMotor Ocular Single

Fourth Cranial Nerve Palsy

Key Facts

•Damage to fourth cranial nerve causing vertical misalignment that increases with gaze contralateral to side of palsy and with ipsilateral head tilt

•Common causes:

•reduced perfusion to intracranial segment of the nerve in diabetes or arteriosclerosis (ischemic palsy)

•head trauma

•decompensation of a congenital fourth cranial nerve palsy

•Uncommon causes:

•compression by intracranial mass lesions

•non-infectious, infectious, or neoplastic meningitis

•Brain MRI indicated if an ischemic palsy is not a plausible diagnosis

Clinical Findings

•Vertical diplopia sometimes with torsional misalignment of images

•Vertical misalignment that increases with gaze contralateral to side of palsy and with ipsilateral head tilt

•Excyclodeviation on double Maddox rod test (>10º suggests bilateral fourth cranial nerve palsies)

•Increased vertical fusional amplitudes suggest decompensated congenital disorder

Ancillary Testing

•Intravenous edrophonium chloride test, repetitive stimulation and single-fiber electromyography, and/or acetylcholine receptor antibodies are indicated if myasthenia gravis is a consideration

•Orbit imaging if there are clinical signs of orbitopathy

•MRI/magnetic resonance angiography or CT/CT angiography indicated if ischemic palsy is not a plausible diagnosis

Differential Diagnosis

•Graves disease

•Orbital myositis

•Orbital tumor

•Traumatic orbitopathy

•Myasthenia gravis

•Third cranial nerve palsy

•Skew deviation

Treatment

• In palsy stable for ≥9 months, consider extraocular muscle surgery

Prognosis

•Ischemic palsies resolve completely within 3 months

•Non-ischemic palsies have variable resolution depending on cause and degree of damage

•Extraocular muscle surgery is nearly always successful in providing an adequate zone of single binocular vision

A

B

Fig. 6.3 Right fourth cranial nerve palsy. In primary position (straight ahead gaze), the right eye is higher than the left eye (right hypertropia). In right gaze and left head tilt, the hypertropia diminishes; in left gaze and right head tilt, the hypertropia increases (head tilts shown in B).

Palsy Nerve Cranial Fourth