- Ataxia (HP:0001251): 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). Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:98759)
- Gait disturbance (HP:0001288): The term gait disturbance can refer to any disruption of the ability to walk. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:98759)
- Torticollis (HP:0000473): Involuntary contractions of the neck musculature resulting in an abnormal posture of or abnormal movements of the head. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98759)
- Blepharospasm (HP:0000643): A focal dystonia that affects the muscles of the eyelids and brow, associated with involuntary recurrent spasm of both eyelids. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98759)
- Atypical behavior (HP:0000708): Atypical behavior is an abnormality in a person's actions that can be controlled or modulated by the will of the individual. While abnormal behaviors can be difficult to control, they are distinct from other abnormal actions that cannot be affected by the individual's will. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98759)
- Spasticity (HP:0001257): A motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes with increased muscle tone, exaggerated (hyperexcitable) tendon reflexes. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98759)
- Mental deterioration (HP:0001268): Loss of previously present mental abilities, generally in adults. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98759)
- Cerebellar atrophy (HP:0001272): Cerebellar atrophy is defined as a cerebellum with initially normal structures, in a posterior fossa with normal size, which displays enlarged fissures (interfolial spaces) in comparison to the foliae secondary to loss of tissue. Cerebellar atrophy implies irreversible loss of tissue and result from an ongoing progressive disease until a final stage is reached or a single injury, e.g. an intoxication or infectious event. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98759)
- Parkinsonism (HP:0001300): Characteristic neurologic anomaly resulting from degeneration of dopamine-generating cells in the substantia nigra, a region of the midbrain, characterized clinically by shaking, rigidity, slowness of movement and difficulty with walking and gait. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98759)
- Dystonia (HP:0001332): An abnormally increased muscular tone that causes fixed abnormal postures. There is a slow, intermittent twisting motion that leads to exaggerated turning and posture of the extremities and trunk. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98759)
- Rigidity (HP:0002063): Continuous involuntary sustained muscle contraction. When an affected muscle is passively stretched, the degree of resistance remains constant regardless of the rate at which the muscle is stretched. This feature helps to distinguish rigidity from muscle spasticity. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98759)
- Chorea (HP:0002072): Chorea (Greek for 'dance') refers to widespread arrhythmic involuntary movements of a forcible, jerky and restless fashion. It is a random-appearing sequence of one or more discrete involuntary movements or movement fragments. Movements appear random because of variability in timing, duration or location. Each movement may have a distinct start and end. However, movements may be strung together and thus may appear to flow randomly from one muscle group to another. Chorea can involve the trunk, neck, face, tongue, and extremities. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98759)
- Neuronal loss in central nervous system (HP:0002529). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98759)
- Involuntary movements (HP:0004305): Involuntary contractions of muscle leading to involuntary movements of extremities, neck, trunk, or face. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98759)
- Generalized cerebral atrophy/hypoplasia (HP:0007058): Generalized atrophy or hypoplasia of the cerebrum. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98759)
- Abnormal pyramidal sign (HP:0007256): Functional neurological abnormalities related to dysfunction of the pyramidal tract. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98759)
- Atrophy/Degeneration affecting the brainstem (HP:0007366). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98759)
- Cerebellar Purkinje layer atrophy (HP:0012082): Atrophy of the cerebellum affecting primarily the Purkinje cell layer. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98759)
- Writer's cramp (HP:0002356): A focal dystonia of the fingers, hand, and/or forearm that appears when the affected person attempts to do a task that requires fine motor movements such as writing or playing a musical instrument. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98759)
These phenotypes are associated with the disease Spinocerebellar ataxia type 17 (ORPHA:98759).