Supranuclear Palsy and Moebius Syndrome Flashcards
Why do we have eye movements?
To maximize vision, hold images still on the retina, analyze objects optimally, compensate for head movements, and achieve binocular vision.
Two principal types of eye movements:
Steady image on retina: Vestibular, optokinetic, smooth pursuit.
Change line of sight: Saccades, pursuit, vergences.
What is a supranuclear palsy?
A lesion in the eye movement control pathways above the cranial nerve nuclei, leading to gaze palsies.
Horizontal saccades pathway:
From FEF through internal capsule, decussates in midbrain and terminates in PPRF. Parietal pathway decussates to the superior colliculus before PPRF.
Vertical saccades pathway:
Requires bilateral stimulation of FEF and passes through the rostral interstitial nucleus of the MLF (riMLF).
Lesion effects on horizontal saccades:
Before decussation: Loss of conjugate gaze to contralateral side.
At decussation: Loss of movement to both sides.
Below decussation (pons): Ipsilateral gaze loss.
Global paralysis (Roth Bielschowsky syndrome):
Total loss of saccades and pursuit, but intact VOR and vestibular nystagmus, due to a lesion in the upper midbrain.
Frontal lobe lesions (unilateral):
Loss of saccades to the contralateral side and visual hemifield neglect.
Occipital lobe lesions:
Unilateral lesions cause contralateral hemianopia and search saccades when attempting to look into the affected field.
Parieto-occipital lesions:
Unilateral lesions lead to failure of smooth pursuit on the affected side and cogwheel pursuit.
Progressive Supranuclear Palsy (PSP):
Affects vertical saccades (upgaze/downgaze), eventually causes complete ophthalmoplegia, and presents with balance issues and swallowing difficulties.
Parkinson’s disease:
Defective upgaze and slow vertical saccades with impaired vergences (particularly divergence).
Huntington’s chorea:
Causes defective saccades, especially during the early part of upgaze.
Parinaud’s syndrome:
Loss of upgaze, Collier’s sign (lid retraction), convergence-retraction nystagmus, and skew deviation.
Hydrocephalus:
Vertical upgaze palsy with the “setting sun sign” due to increased intracranial pressure.
Key clinical observations:
Check gait, facial weakness, head thrusts, AHP, and consciousness.
Ocular observations:
Eye position, pupil abnormalities, ptosis, nystagmus types, globe position (proptosis or enophthalmos).
Eye movement assessments:
Test saccades, smooth pursuit, VOR, OKN, and uniocular movements.
Caloric testing:
Warm water causes eye deviation to the same side; cold water causes deviation to the opposite side.
Bells phenomenon:
Elevation of eyes during forced lid closure indicates intact 3rd nerve and superior rectus.
Orthoptic treatment
Monitor condition, prism therapy, manage AHP, occlusion for diplopia, and ptosis props.
Multidisciplinary approach:
Collaborate with ophthalmology, neurology, and medical teams to assess progress and adjust care.
Definition of Moebius syndrome:
A congenital, non-progressive disorder with bilateral 6th and 7th cranial nerve palsies, often part of the congenital cranial dysinnervation disorders (CCDD).
Etiology of Moebius syndrome:
Developmental defects, hypoxic/traumatic insult in utero, vascular malformations, or genetic predisposition.
Clinical features of Moebius syndrome:
Lack of facial expression, poor lid closure, esotropia, and abduction limitation.
Associated systemic features:
Limb defects (e.g., clubfoot, syndactyly), hearing loss, feeding difficulties, delayed speech, and microstomia.
6th cranial nerve involvement:
Marked esotropia, cross-fixation, impaired convergence, and V pattern strabismus.
7th cranial nerve involvement:
Bilateral facial palsy with absent facial expression and poor lid closure.
Vertical gaze in Moebius syndrome:
Intact in most cases, but 25% may have impairments.
Exposure keratitis management:
Use lubricants and lid taping at night to prevent corneal abrasions.
Differentiating moebius syndrome from other conditions:
Infantile myotonic dystrophy, Duane’s syndrome, congenital ocular motor apraxia, and horizontal gaze palsy.
What is congenital ocular motor apraxia (COMA):
Absence of voluntary horizontal saccades with head thrusting maneuvers to initiate fixation.
Why is refractive correction used:
To address astigmatism and amblyopia early to optimize vision.
Which surgery is used
Bilateral medial rectus recessions for esotropia and vertical muscle transpositions for improved cosmesis.
What does the MDT approach include
Include genetic counseling and developmental monitoring for comprehensive care.
Prognosis in Moebius syndrome:
Stable over time with tailored interventions for ocular and systemic complications.
PSP progression:
Gradual decline, loss of vertical and later horizontal movements, with significant mortality within 6 years.
Improvement with age (e.g., COMA):
Some patients develop compensatory strategies and gain better control over time.
Imaging techniques:
MRI/CT for identifying structural lesions, such as hydrocephalus or pinealoma.
Electrodiagnostic tools use:
Eye movement recordings for documenting saccadic latency, accuracy, and nystagmus waveforms.
