Search

Ataxia is not only due to cerebellar lesions, but also due to non-cerebellar lesions such as those in the brain, spinal cord, dorsal root (DR), peripheral nerve. In this article, optic ataxia is excluded and 'vestibular ataxia' is briefly referred. Non-cerebellar ataxias are generically called sensory ataxia or posterior column ataxia. However, since non-cerebellar lesions, e.g. frontal lobe lesions, may develop "cerebellar-like ataxia" (Hirayama, 2010). At the same time, non-posterior column lesions, e.g. parietal lobe lesion, can show "posterior column-like ataxia". From these viewpoints, I here describe various non-cerebellar ataxia in some disorders such as tabes dorsalis and sensory neuropathies and emphasize a role of a peripheral sensory input to the cerebellum via the DR ganglia and spinocerebellar tract for sensory ataxia because there is the International Consensus (2016) that the ataxia in Miller Fisher syndrome is suggested cerebellar-like clinicophysiologically.

We report the case of a 73-year-old right-handed female with a right parietal cerebral infarction and presented symptoms that were challenging to differentiate between alien hand sign (AHS) and sensory ataxia. She presented to our emergency department with chief complaints of abnormal involuntary movements and a feeling of foreignness on her left upper limb. The first neurological examination revealed left spatial neglect, left-side sensory impairment that included superficial and deep sensations, left limb-kinetic apraxia, and left limb ataxia. Furthermore, her symptoms and complaints had characteristics of AHS that includes a sensation that her left upper limb dose not belong to herself and an abnormal behavior of left hand that is contrary to her own intent. Brain MRI revealed an acute cerebral infarction confined to the right postcentral gyrus. This case highlights that sensory ataxia due to the disturbance of deep sensation might present symptoms similar to AHS. Previous studies suggested the involvement of the disturbance of somatosensory pathway in posterior-variant AHS. Therefore, a precise distinction between AHS and sensory ataxia, especially in posterior-variant AHS, is imperative to avoid confusion regarding the term "alien hand sign."