- Olivopontocerebellar atrophy (HP:0002542): Neuronal degeneration in the cerebellum, pontine nuclei, and inferior olivary nucleus. Evidence: IEA. (OMIM:164400)
- Decreased motor nerve conduction velocity (HP:0003431): A type of decreased nerve conduction velocity that affects the motor neuron. Evidence: PCS. Frequency: 2/9. (PMID:9448569)
- Gaze-evoked nystagmus (HP:0000640): Nystagmus made apparent by looking to the right or to the left. Evidence: TAS. (OMIM:164400)
- Hypotonia (HP:0001252): Hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle). Even when relaxed, muscles have a continuous and passive partial contraction which provides some resistance to passive stretching. Hypotonia thus manifests as diminished resistance to passive stretching. Hypotonia is not the same as muscle weakness, although the two conditions can co-exist. Evidence: IEA. (OMIM:164400)
- Muscle spasm (HP:0003394): Sudden and involuntary contractions of one or more muscles. Evidence: PCS. Frequency: 3/5. (PMID:14967775)
- Distal muscle weakness (HP:0002460): Reduced strength of the musculature of the distal extremities. Evidence: PCS. Frequency: 2/5. (PMID:14967775)
- Generalized hypotonia (HP:0001290): Generalized muscular hypotonia (abnormally low muscle tone). Evidence: TAS. (OMIM:164400)
- Fasciculations (HP:0002380): 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. Evidence: PCS. Frequency: 1/5. (PMID:14967775)
- Nystagmus (HP:0000639): Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms. Evidence: IEA. (OMIM:164400)
- Slow saccadic eye movements (HP:0000514): An abnormally slow velocity of the saccadic eye movements. Evidence: IEA. (OMIM:164400)
- Dorsal column degeneration (HP:0007006). Evidence: IEA. (OMIM:164400)
- Muscle weakness (HP:0001324): Reduced strength of muscles. Evidence: PCS. Frequency: 1/5. (PMID:14967775)
- Proximal muscle weakness (HP:0003701): A lack of strength of the proximal muscles. Evidence: PCS. Frequency: 1/5. (PMID:14967775)
- Genetic anticipation with paternal anticipation bias (HP:0003744): A type of genetic anticipation observed predominantly upon transmission from affected males. Evidence: IEA. (OMIM:164400)
- Impaired pain sensation (HP:0007328): Reduced ability to perceive painful stimuli. Evidence: PCS. Frequency: 2/5. (PMID:14967775)
- Skeletal muscle atrophy (HP:0003202): The presence of skeletal muscular atrophy (which is also known as amyotrophy). Evidence: IEA. (OMIM:164400)
- Paresthesia (HP:0003401): Abnormal sensations such as tingling, pricking, or numbness of the skin with no apparent physical cause. Evidence: PCS. Frequency: 1/5. (PMID:14967775)
- Truncal ataxia (HP:0002078): Truncal ataxia is a sign of ataxia characterized by instability of the trunk. It usually occurs during sitting. Evidence: TAS. (OMIM:164400)
- Babinski sign (HP:0003487): 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. Evidence: IEA. (OMIM:164400)
- Impaired distal tactile sensation (HP:0006937): A reduced sense of touch (tactile sensation) on the skin of the distal limbs. This is usually tested with a wisp of cotton or a fine camel's hair brush, by asking patients to say 'now' each time they feel the stimulus. Evidence: PCS. Frequency: 2/5. (PMID:14967775)
- Dilated fourth ventricle (HP:0002198): An abnormal dilatation of the fourth cerebral ventricle. Evidence: TAS. (OMIM:164400)
- Dysarthria (HP:0001260): 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. Evidence: IEA. (OMIM:164400)
- Dysdiadochokinesis (HP:0002075): A type of ataxia characterized by the impairment of the ability to perform rapidly alternating movements, such as pronating and supinating his or her hand on the dorsum of the other hand as rapidly as possible. Evidence: IEA. (OMIM:164400)
- 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: IEA. (OMIM:164400)
- Progressive cerebellar ataxia (HP:0002073). Evidence: PCS. (PMID:14967775)
- Limb ataxia (HP:0002070): A kind of ataxia that affects movements of the extremities. Evidence: TAS. (OMIM:164400)
- Abnormality of extrapyramidal motor function (HP:0002071): A neurological condition related to lesions of the basal ganglia leading to typical abnormalities including akinesia (inability to initiate changes in activity and perform volitional movements rapidly and easily), muscular rigidity (continuous contraction of muscles with constant resistance to passive movement), chorea (widespread arrhythmic movements of a forcible, rapid, jerky, and restless nature), athetosis (inability to sustain the muscles of the fingers, toes, or other group of muscles in a fixed position), and akathisia (inability to remain motionless). Evidence: PCS. (OMIM:164400)
- Impaired proprioception (HP:0010831): A loss or impairment of the sensation of the relative position of parts of the body and joint position. Evidence: PCS. Frequency: 1/5. (PMID:14967775)
- Decreased amplitude of sensory action potentials (HP:0007078): A reduction in the amplitude of sensory nerve action potential. This feature is measured by nerve conduction studies. Evidence: PCS. Frequency: 9/9. (PMID:9448569)
- Optic atrophy (HP:0000648): Atrophy of the optic nerve. Optic atrophy results from the death of the retinal ganglion cell axons that comprise the optic nerve and manifesting as a pale optic nerve on fundoscopy. Evidence: IEA. (OMIM:164400)
- Dysmetric saccades (HP:0000641): The controller signal for saccadic eye movements has two components: the pulse that moves the eye rapidly from one point to the next, and the step that holds the eye in the new position. When both the pulse and the step are not the correct size, a dysmetric refixation eye movement results. Evidence: TAS. (OMIM:164400)
- 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. (OMIM:164400)
- Spinocerebellar tract degeneration (HP:0002503). Evidence: PCS. (OMIM:164400)
- Autosomal dominant inheritance (HP:0000006): A mode of inheritance that is observed for traits related to a gene encoded on one of the autosomes (i.e., the human chromosomes 1-22) in which a trait manifests in heterozygotes. In the context of medical genetics, an autosomal dominant disorder is caused when a single copy of the mutant allele is present. Males and females are affected equally, and can both transmit the disorder with a risk of 50% for each child of inheriting the mutant allele. Evidence: PCS. (PMID:7951322)
- Scanning speech (HP:0002168): An abnormal pattern of speech in which the words are as if measured or scanned; there is a pause after every syllable, and the syllables themselves are pronounced slowly. Evidence: IEA. (OMIM:164400)
- Dysmetria (HP:0001310): 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. Evidence: IEA. (OMIM:164400)
- Distal amyotrophy (HP:0003693): Muscular atrophy affecting muscles in the distal portions of the extremities. Evidence: TAS. (OMIM:164400)
- Impaired horizontal smooth pursuit (HP:0001151): An abnormality of ocular smooth pursuit characterized by an impairment of the ability to track horizontally moving objects. Evidence: TAS. (OMIM:164400)
- Cognitive impairment (HP:0100543): Abnormal cognition is characterized by deficits in thinking, reasoning, or remembering. Evidence: PCS. (OMIM:164400)
- Spinocerebellar atrophy (HP:0007263): Atrophy affecting the cerebellum and the spinocerebellar tracts of the spinal cord. Evidence: IEA. (OMIM:164400)
- Urinary bladder sphincter dysfunction (HP:0002839): Abnormal function of a sphincter of the urinary bladder. Evidence: IEA. (OMIM:164400)
- Decreased sensory nerve conduction velocity (HP:0003448): Reduced speed of conduction of the action potential along a sensory nerve. Evidence: PCS. Frequency: 1/9. (PMID:9448569)
- Hyperreflexia (HP:0001347): Hyperreflexia is the presence of hyperactive stretch reflexes of the muscles. Evidence: IEA. (OMIM:164400)
- Dysphagia (HP:0002015): Difficulty in swallowing. Evidence: IEA. (OMIM:164400)
- Bulbar palsy (HP:0001283): Bulbar weakness (or bulbar palsy) refers to bilateral impairment of function of the lower cranial nerves IX, X, XI and XII, which occurs due to lower motor neuron lesion either at nuclear or fascicular level in the medulla or from bilateral lesions of the lower cranial nerves outside the brain-stem. Bulbar weakness is often associated with difficulty in chewing, weakness of the facial muscles, dysarthria, palatal weakness and regurgitation of fluids, dysphagia, and dysphonia. Evidence: IEA. (OMIM:164400)
- Impaired vibratory sensation (HP:0002495): A decrease in the ability to perceive vibration. Clinically, this is usually tested with a tuning fork which vibrates at 128 Hz and is applied to bony prominences such as the malleoli at the ankles or the metacarpal-phalangeal joints. There is a slow decay of vibration from the tuning fork. The degree of vibratory sense loss can be crudely estimated by counting the number of seconds that the examiner can perceive the vibration longer than the patient. Evidence: PCS. Frequency: 15/15. (OMIM:164400;PMID:14967775)
- Adult onset (HP:0003581): Onset of disease manifestations in adulthood, defined here as at the age of 16 years or later. Evidence: PCS. Frequency: 6/6. (PMID:14967775)
- Areflexia (HP:0001284): Absence of neurologic reflexes such as the knee-jerk reaction. Evidence: PCS. (OMIM:164400)
- Peripheral neuropathy (HP:0009830): Peripheral neuropathy is a general term for any disorder of the peripheral nervous system. The main clinical features used to classify peripheral neuropathy are distribution, type (mainly demyelinating versus mainly axonal), duration, and course. Evidence: TAS. (OMIM:164400)
- Supranuclear ophthalmoplegia (HP:0000623): A vertical gaze palsy with inability to direct the gaze of the eyes downwards. Evidence: IEA. (OMIM:164400)
- Optic disc pallor (HP:0000543): A pale yellow discoloration of the optic disc (the area of the optic nerve head in the retina). The optic disc normally has a pinkish hue with a central yellowish depression. Evidence: TAS. (OMIM:164400)
These phenotypes are associated with the disease spinocerebellar ataxia type 1 (OMIM:164400).