| Typical Onset | Typically adolescence (mean age 12-15 years) |
| Nonsense mutations | ~40% — premature stop codons, typically severe phenotype |
| Missense mutations | ~35% — may retain partial function, variable severity |
| Frameshift mutations | ~15% — insertions/deletions causing truncations |
| Splice site mutations | ~10% — abnormal mRNA processing |
| Two truncating mutations | Earlier onset (mean 7 years), more rapid progression |
| Missense compound heterozygous | Later onset, slower progression |
| Residual senataxin activity | Correlates with milder phenotype |
| Progressive cerebellar ataxia | Gait instability, limb incoordination, dysarthria (scanning speech) |
| Oculomotor apraxia | Difficulty initiating voluntary eye movements, especially horizontal gaze — patients use head thrusts to compensate |
| Elevated AFP | Persistent elevation of serum alpha-fetoprotein is a key diagnostic marker (normal in A-T) |
| Sensorimotor neuropathy | Distal weakness, reduced or absent deep tendon reflexes |
| Databases | OMIMOrphanetClinicalTrialsPubMed |