What are the characteristics, causes, and examination methods for supranuclear gaze palsy and nuclear gaze palsy?

Supranuclear and Nuclear Gaze Palsy: Characteristics, Causes, and Examination

Key Distinction Between Supranuclear and Nuclear Gaze Palsies

Supranuclear gaze palsies result from lesions above the level of the ocular motor nerve nuclei and can be overcome with vestibulo-ocular reflex testing (oculocephalic maneuvers), whereas nuclear gaze palsies involve damage to the cranial nerve nuclei themselves (III, IV, VI) and cannot be overcome with these maneuvers. 1

Supranuclear Gaze Palsy

Defining Characteristics

• Inability to move eyes in a specific direction due to neurological damage above the brainstem nuclei 2
• Eyes cannot move past midline in the affected direction even with vestibulo-ocular reflex testing 2
• Characterized by gaze palsies, tonic gaze deviation, saccadic and smooth pursuit disorders, vergence abnormalities, nystagmus, and ocular oscillations 1
• Limitation in range of motion is typically worse with saccades than with smooth pursuit 3
• Loss of quick phases of optokinetic nystagmus 3

Major Causes

Progressive Supranuclear Palsy (PSP)

• Most common cause of chronic vertical supranuclear gaze palsy 3
• Postural instability with supranuclear gaze palsy, accompanied by varying degrees of cognitive, behavioral, or other movement symptoms 4
• Usually caused by FTLD-PSP (frontotemporal lobar degeneration with tau pathology) 4
• Vertical gaze palsy affects downward gaze more than upward, often with absent optokinetic nystagmus or slowed downward saccades 2, 5
• Saccades are slower and hypometric, both up and down 6
• Impaired vergence and inability to modulate the linear vestibulo-ocular reflex appropriately for viewing distance 6
• Early postural instability with frequent falls is characteristic 5

Acute Brainstem Stroke

• Most common cause of acute-onset supranuclear gaze palsy 3
• Brainstem infarction affecting the saccade-generating network 3

Internuclear Ophthalmoplegia (INO)

• Due to lesion of the medial longitudinal fasciculus 1
• Caused by multiple sclerosis in younger patients, particularly when bilateral 1
• Usually of vascular origin in elderly patients 1
• Demyelinating plaque in multiple sclerosis is primary consideration in younger patients; stroke in older patients presenting acutely 4

Other Causes

• Corticobasal degeneration (CBD) - sometimes causes PSP syndrome 4
• Lewy body disease - rarely causes PSP syndrome 4
• Tumor, hemorrhage, and infection - can cause internuclear ophthalmoplegia 4

Critical Examination Techniques

Vestibulo-Ocular Reflex (Oculocephalic Maneuvers)

• The definitive test to distinguish supranuclear from nuclear/infranuclear pathology 2, 1
• If oculocephalic maneuvers move the eyes appropriately past midline, the lesion is supranuclear 1
• In supranuclear palsy, eyes remain fixed and cannot cross midline despite head turning 2

Saccade Testing

• Assess velocity and amplitude of vertical and horizontal saccades 5, 3
• In PSP, vertical saccades are slow and hypometric 6, 7
• Large amplitude saccade attempts may result in "fractionated" saccades 7

Optokinetic Nystagmus

• Assess for presence or absence of vertical optokinetic nystagmus 5
• Loss of quick phases indicates supranuclear pathology 3
• In PSP, optokinetic nystagmus is often absent 2, 5

Smooth Pursuit Testing

• Pursuit eye movements become saccadic in PSP 7
• Range of motion limitation is less pronounced with smooth pursuit than with saccades 3

Postural Stability Assessment

• Early postural instability with frequent falls is characteristic of PSP 5
• Assess gait disturbance, bradykinesia, and rigidity 5

Vergence Testing

• Impaired vergence is prominent in PSP 6

Nuclear Gaze Palsy

Defining Characteristics

• Results from damage to cranial nerve nuclei III, IV, or VI within the brainstem 4, 1
• Cannot be overcome by vestibulo-ocular reflex testing 2, 1
• Eyes remain fixed in the affected direction even with oculocephalic maneuvers 2

Major Causes

Cranial Nerve III (Oculomotor) Nucleus Lesions

• Pupil-involving palsies suggest vascular compression (e.g., aneurysm) 4
• Pupil-sparing palsies suggest vasculopathic etiologies (e.g., diabetes, hypertension) 4

Cranial Nerve IV (Trochlear) Nucleus Lesions

• Most often caused by trauma 4
• Rarely caused by nerve sheath tumors 4

Cranial Nerve VI (Abducens) Nucleus Lesions

• May be caused by lesions within the prepontine cistern, skull base, cavernous sinus, or sella 4
• May occur with increased intracranial pressure without direct nerve compression 4
• Sixth nerve palsy produces horizontal gaze limitation but is an infranuclear problem, not a supranuclear gaze palsy 2

Multiple Ipsilateral Cranial Nerve Palsies

• Affecting cranial nerves III, IV, and VI suggests lesion at cavernous sinus or orbital apex 4
• Can occur with pathology in basilar subarachnoid space from infectious meningitis (TB, fungal, Lyme disease) or noninfectious causes (sarcoid, neoplasm, perineural or leptomeningeal tumor spread) 4

Orbital Trauma

• Rectus or oblique muscle avulsion, partial or complete "loss," flap tear, hemorrhage, edema, or paresis 4
• Orbital hemorrhage or edema, soft tissue swelling, and fracture of orbital bones with or without entrapment 4
• Diplopia occurs in 58% to 68% of blowout fractures 4

Critical Examination Techniques

Forced Duction and Forced Generation Testing

• Helps distinguish restriction from paresis of extraocular muscles 4

Cover Testing

• Perform at near and distance in primary and secondary gaze positions 4
• Evaluate torsion for patients with vertical misalignment 4

Versions and Ductions Assessment

• Detailed sensorimotor exam with attention to versions, ductions, saccades, pursuit, vergence, and near reflex 4
• Alignment testing in multiple gaze positions with attention to primary and secondary deviations 4

Pupillary Examination

• Critical for distinguishing pupil-involving from pupil-sparing third nerve palsies 4

Imaging Studies

• MRI of the head without and with contrast including small field-of-view high-resolution T2-weighted images of cranial nerves is preferred for suspected nuclear pathology 4
• CTA or MRA indicated when vascular compression from aneurysm is suspected 4
• CT preferred over MRI if concern for ferrous-metallic foreign body or orbital fracture 4
• High-resolution orbital imaging useful for evaluation of mechanical causes 4

Critical Pitfalls to Avoid

• Do not confuse gaze preference with gaze palsy - gaze preference describes eyes that rest in a deviated position but can move past midline with vestibulo-ocular reflex, whereas true gaze palsy cannot 2
• Do not miss life-threatening causes - entrapped muscle causing oculocardiac reflex (bradycardia, heart block, dizziness, nausea, vomiting, loss of consciousness) requires urgent medical and surgical treatment 4
• Do not delay vascular imaging in pupil-involving third nerve palsy - vascular compression from adjacent aneurysm is the primary consideration 4
• Do not attribute all vertical gaze palsies to PSP - acute brainstem stroke is the most common cause of acute-onset supranuclear gaze palsy 3