bulbar palsy

Spinocerebellar Ataxia 1

Clinical Characteristics
Ocular Features: 

Early manifestations include gaze-evoked nystagmus and saccadic hypermetria.  Ophthalmoplegia develops later in the disease process.  Some patients experience a decrease in acuity and dyschromatopsia.  The ERG shows evidence of generalized rod and cone photoreceptor dysfunction in some patients.  Optic atrophy, central scotomas, central RPE changes, retinal arteriolar attenuation, and blepharospasm have also been reported.

Time-domain OCT has revealed microscopic changes in the macula with thinning of the inner-outer segment junction and nuclear layer in areas with RPE hypopigmentation. 

Systemic Features: 

This is a progressive cerebellar syndrome characterized by systems of ataxia, dysarthria, and bulbar palsy.  Speech is often scanning and explosive.  DTRs can be exaggerated, and dysmetria is common.  The mean age of onset is about age 40.  Some cognitive decline may occur.  Muscle atrophy, and symptoms of peripheral neuropathy can be present.  MRI shows atrophy in the cerebellum, spinal cord, and brainstem.  There is considerable variation in clinical expression.  Individuals with adult onset of symptoms can survive for 10-30 years whereas those with a juvenile-onset often do not live beyond the age of 16 years.

Genetics

This disorder is caused by an expanded CAG repeat in the ataxin-1 gene (ATXN1) at 6p23.  It is an autosomal dominant disorder.  Alleles with 39-44 or more CAG repeats are likely to be associated with symptoms. 

A male bias and the phenomenon of anticipation have been demonstrated in this disorder as in spinocerebellar ataxia 7 (SCA7) (164500), in which affected offspring of males with SCA develop disease earlier and symptoms progress more rapidly than in offspring of females.  This is often explained by the fact that males generally transmit a larger number of CAG repeats.

SCA7 (164500), also inherited in an autosomal dominant pattern and caused by expanded CAG repeats on chromosome 3, has many similar ocular and neurologic features.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Supportive care is often required.          

References
Article Title: 

Corneal Dystrophy, Lattice Type II

Clinical Characteristics
Ocular Features: 

This is a systemic amyloidosis disorder with significant corneal disease.  The corneal stroma contains linear deposits which are more discrete, more peripheral, more delicate, and more radial than those in lattice type I with which it is sometimes confused.  There is also less accumulation of amorphous amyloid material than in type I.  The onset is often later as well, and rarely seen in childhood.  Corneal sensitivity is reduced.  Vision is less affected than in type I lattice dystrophy and patients rarely require keratoplasty, and, if so, later in life.

Amyloid deposits are found in the cornea, sclera, choroid, lacrimal gland, ciliary nerves, and adnexal blood vessels.  Ptosis and extraocular muscle dysfunction is not significant.

Systemic Features: 

Amyloid deposits are found throughout the body including blood vessels, heart, kidney, skin and nerves.  A "mask-like" facies with a protruding lower lip, dry itchy skin, peripheral and cranial neuropathy, and renal failure are clinical features but often have their onset late in life.  Facial paralysis and bulbar palsy may be the result.

Genetics

While this is considered an autosomal dominant disorder, presumed homozygous cases have been reported in Finland where the first cases were described.  These cases seem to have more severe disease with an earlier onset than found among patients with heterozygous mutations.  Mutations in the GSN gene located at 9q34 are responsible.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Penetrating keratoplasty can be beneficial but is rarely needed for visual rehabilitation.  The amyloid deposits may recur in the donor tissue.  The reduced corneal sensitivity secondary to neural involvement increases the risk of post-operative neurotrophic epithelial defects.

References
Article Title: 

Hereditary gelsolin amyloidosis

Kiuru-Enari S, Haltia M. Hereditary gelsolin amyloidosis. Handb Clin Neurol. 2013;115:659-81. PubMed PMID: 23931809.

PubMed ID: 
23931809
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