Spinocerebellar ataxia type 1 is an autosomal dominant genetic disease in which progressive central nervous system degeneration (primarily of the cerebellum) results in the appearance of gait disorders, dysarthria, and severe motor impairment. The severity of the disorder and clinical progression markedly varies from patient to patient. The diagnosis is made on clinical grounds, findings obtained from a detailed family history, and genetic testing to confirm ataxin-1 mutations.
Spinocerebellar ataxias (SCAs) are a group of more than 40 distinct disorders of progressive neuronal degeneration, principally involving the cerebellum and the motor tracts involved in signaling to and from this part of the central nervous system    . Each type arises due to a specific genetic mutation and in the case of spinocerebellar ataxia type 1 (SCA1), the ataxin-1 gene (located on chromosome 6) is expanded by trinucleotide repeats (CAG)   , which through still unexplained mechanisms, leads to a variable degree of central nervous system damage. The onset of symptoms is reported to be around 30-40 years of age in the majority of patients, while gender predilection has not been established  . Symptoms related to the function of the cerebellum are the cornerstone of spinocerebellar ataxia type 1, with the inability to control body movements (ataxia) resulting in gait impairment and an improper balance being the main complaints  . In addition, dysarthria and ocular symptoms (diplopia, difficulties with focusing objects, saccadic nystagmus, gaze palsies, blepharospasm, and ptosis) are frequently encountered in this patient population   . Some reports have identified cognitive dysfunction (memory impairment, defects in executive functioning) and focal dystonias (writer's cramp) in the clinical presentation  . Unfortunately, ataxia eventually affects all four limbs and necessitates the use of wheelchairs within 15-20 years in virtually all individuals who suffer from this condition .
Because of the rare occurrence of spinocerebellar ataxia type 1 in clinical practice (1-2 per 100,000 individuals) , the diagnosis may be difficult to establish without a comprehensive clinical investigation. One of the most important components of the workup is a thorough patient history, during which the familial presence of symptoms can be the first sign pointing toward an inherited disorder. The age of onset, as well as the progression of symptoms, should be noted. A detailed physical examination must follow and the physician must particularly focus on the neurological exam and evaluation of the cerebellum. A wide stance, gait difficulties, and tremor (intentional) on finger-nose testing are some of the main findings in patients with spinocerebellar ataxia type 1 , whereas assessment of speech and eye movement to identify dysarthria and associated anomalies, respectively, are equally important steps. Once sufficient evidence toward this disorder is attained, genetic testing may be indicated  . Confirmation of trinucleotide repeats on the ataxin-1 gene through various molecular methods are a definite measure for establishing a diagnosis of spinocerebellar ataxia type 1  .