Spinocerebellar ataxia type 36

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Spinocerebellar ataxia type 36 (SCA36) is a condition characterized by progressive problems with movement that typically begin in mid-adulthood. People with this condition initially experience problems with coordination and balance (ataxia). Affected individuals often have exaggerated reflexes (hyperreflexia) and problems with speech (dysarthria). They also usually develop muscle twitches (fasciculations) of the tongue and over time, the muscles in the tongue waste away (atrophy). These tongue problems can cause difficulties swallowing liquids. As the condition progresses, individuals with SCA36 develop muscle atrophy in the legs, forearms, and hands. Another common feature of SCA36 is the atrophy of specialized nerve cells that control muscle movement (motor neurons), which can contribute to the tongue and limb muscle atrophy in affected individuals.

Some people with SCA36 have abnormalities of the eye muscles, which can lead to involuntary eye movements (nystagmus), rapid eye movements (saccades), trouble moving the eyes side-to-side (oculomotor apraxia), and droopy eyelids (ptosis). Sensorineural hearing loss, which is hearing loss caused by changes in the inner ear, may also occur in people with SCA36.

Brain imaging of people with SCA36 shows progressive atrophy of various parts of the brain, particularly within the cerebellum, which is the area of the brain involved in coordinating movements. Over time, the loss of cells in the cerebellum causes the movement problems characteristic of SCA36. In older affected individuals, the frontal lobes of the brain may show atrophy resulting in loss of executive function, which is the ability to plan and implement actions and develop problem-solving strategies.

Signs and symptoms of SCA36 typically begin in a person's forties or fifties but can appear anytime during adulthood. People with SCA36 have a normal lifespan and are usually mobile for 15 to 20 years after they are diagnosed.

ORPHANET DEFINITION An autosomal dominant cerebellar ataxia type 1 that characterized by gait and limb ataxia, lower limb spasticity, dysarthria, muscle fasiculations, tongue atrophy and hyperreflexia.

Inheritance

From: MedlinePlus Genetics, National Library of Medicine

Autosomal dominant

Frequency in the source

From: MedlinePlus Genetics, National Library of Medicine

Reported family(ies): 100.0; Worldwide. This is a published case count, not prevalence. Point prevalence: Unknown; Worldwide; Class only.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Ataxia · Very frequent (99-80%)

Ataxia refers to impaired coordination of voluntary muscle movement. Cerebellar ataxia refers to ataxia due to dysfunction of the cerebellum. This causes a variety of elementary neurological deficits including asynergy (lack of coordination between muscles, limbs and joints), dysmetria (lack of ability to judge distances that can lead to under- or overshoot in grasping movements), and dysdiadochokinesia (inability to perform rapid movements requiring antagonizing muscle groups to be switched on and off repeatedly).

Dysarthria · Very frequent (99-80%)

Dysarthric speech is a general description referring to a neurological speech disorder characterized by poor articulation. Depending on the involved neurological structures, dysarthria may be further classified as spastic, flaccid, ataxic, hyperkinetic and hypokinetic, or mixed.

Hearing impairment · Very frequent (99-80%)

A decreased magnitude of the sensory perception of sound.

Limb ataxia · Very frequent (99-80%)

A kind of ataxia that affects movements of the extremities.

Truncal ataxia · Very frequent (99-80%)

Truncal ataxia is a sign of ataxia characterized by instability of the trunk. It usually occurs during sitting.

Babinski sign · Frequent (79-30%)

Upturning of the big toe (and sometimes fanning of the other toes) in response to stimulation of the sole of the foot. If the Babinski sign is present it can indicate damage to the corticospinal tract.

Blurred vision · Frequent (79-30%)

Lack of sharpness of vision resulting in the inability to see fine detail.

Dysmetria · Frequent (79-30%)

A type of ataxia characterized by the inability to carry out movements with the correct range and motion across the plane of more than one joint related to incorrect estimation of the distances required for targeted movements.

Fasciculations · Frequent (79-30%)

Fasciculations are observed as small, local, involuntary muscle contractions (twitching) visible under the skin. Fasciculations result from increased irritability of an axon (which in turn is often a manifestation of disease of a motor neuron). This leads to sporadic discharges of all the muscle fibers controlled by the axon in isolation from other motor units.

Gait disturbance · Frequent (79-30%)

The term gait disturbance can refer to any disruption of the ability to walk.

Skeletal muscle atrophy · Frequent (79-30%)

The presence of skeletal muscular atrophy (which is also known as amyotrophy).

Slow saccadic eye movements · Frequent (79-30%)

An abnormally slow velocity of the saccadic eye movements.

Tongue atrophy · Frequent (79-30%)

Wasting of the tongue.

Tongue fasciculations · Frequent (79-30%)

Fasciculations or fibrillation affecting the tongue muscle.

Other findings in the same source

From: Orphanet

Additional reported features include Loss of Purkinje cells in the cerebellar vermis (Frequent (79-30%)); Hyperreflexia (Occasional (29-5%)); Ptosis (Occasional (29-5%)); Attention deficit hyperactivity disorder (Very rare (<4-1%)); Bowel incontinence (Very rare (<4-1%)); Diplopia (Very rare (<4-1%)); Dysphagia (Very rare (<4-1%)); Hand tremor (Very rare (<4-1%)); Head tremor (Very rare (<4-1%)); Intention tremor (Very rare (<4-1%)). This is a selected summary, not a complete description of the condition.

When it may begin

From: MedlinePlus Genetics, National Library of Medicine

Adult

Inheritance in the source

From: MedlinePlus Genetics, National Library of Medicine

Autosomal dominant

Frequency and the population described

From: MedlinePlus Genetics, National Library of Medicine

Reported family(ies): 100.0; Worldwide. This is a published case count, not prevalence. Point prevalence: Unknown; Worldwide; Class only.

Understanding the inheritance label

From: MedlinePlus Genetics

An autosomal dominant pattern means that one altered copy of a relevant gene can be sufficient for the condition. Some affected people inherit the change; others have a new change without an affected parent. The precise finding, family history and condition determine what this means for relatives.

Which doctor should you see?

The suggested department for discussing Spinocerebellar ataxia type 36 is Neurology, with a neurologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Which nervous-system findings help explain the symptoms?
• Would an assessment of walking, communication or daily function be helpful?
• Are rehabilitation or other specialist services relevant?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Spinocerebellar ataxia type 36. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.