Truncal ataxia, also known as “drunken sailor” gait, is a form of ataxia that is characterized by unequal steps, uncertain starts and stops, lateral deviations, and instability of the trunk. It typically occurs during sitting. This type of ataxia is a loss of coordinated muscle movements for maintaining normal posture on the trunk. It is a loss of normal balance of the trunk that causes an increased body sway and dysequilibrium. It primarily affects the trunk causing the patient difficulty in sitting or standing unsupported. It is usually caused by midline damage to the cerebellar vermis and its associated pathways which has an impact on the proximal musculature, most especially the one that is involved in gait stability. It is mainly caused by a midline cerebellar lesion or may also be an attribute of the post-chickenpox cerebellar syndrome.
The cerebellum has 3 functional subdivisions, which feedforward systems and function as feedback. The first subdivision is the vestibulocerebellum. This consists of the connections between the flocculonodular lobe and the vestibular system. Dysfunction of the vestibulocerebellum causes truncal ataxia, nystagmus, and titubation or truncal instability. The second subdivision is the spinocerebellum. This system is composed of the connections between the proprioceptive and cutaneous information that comes from the spinal cord to the paravermis and vermis regions with restorative feedback primarily to the muscles of gait and truncal stability. Dysfunction of this system results in truncal ataxia and gait.The third subdivision of the cerebellum is the cerebrocerebellum. This system is composed of connections from the cerebral cortex to the cerebellar hemispheres then back to the cerebral cortex.
Patients with truncal ataxia cannot stand or sit without any support and they usually have a tendency to fall backward. Truncal tremor or constant jerking of the head and trunk may be evident in an individual affected by truncal ataxia. A persistent incoordination of the truncal axial musculature may produce head tilts, body tilts, or pelvic tilts.
There are many forms of ataxia. Ataxia can either be a disease or a symptom of an underlying condition. Truncal ataxia is a form of ataxia that is more of a symptom rather than a condition. It is a symptom for spinocerebellar ataxia, spastic ataxia, terminal bronchial carcinoma, stroke,
Truncal ataxia is a valuable element in the differential diagnosis of acute vestibular syndrome or AVS. The relationship between the degree of truncal ataxia and stroke has not been systematically studied in patients with AVS.