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.
2What Causes Truncal Ataxia?
Truncal ataxia is usually a result of midline cerebellar disease. Midline lesions can cause truncal ataxia and severe gait.
For some cases of truncal ataxia, it is suggested that truncal ataxia may be caused by the associated ventricular dilation instead of a lesion of the vermis.
The other less common causes of truncal ataxia are the following:
- Alcoholic cerebellar degeneration
- Cerebellar hemorrhage
- Cerebellar abscess
- Posterior fossa tumor
- Friedrich’s ataxia
- Angelman-like syndrome, x-linked
- Chemical poisoning or acrylamide
- Progressive myoclonic 3 epilepsy
- Mental retardation x-linked, South African type
- Neonatal progeroid syndrome
- Olivopontocerebellar atrophy
- Primary torsion dystonia
- Dandy-Walker syndrome
3What are the Symptoms of Truncal Ataxia?
Patients with truncal ataxia experience head tremor and truncal instability that results in oscillatory movements of the trunk and head while standing or sitting. Because of associated hypotonia, they may need back support while sitting.
- Positive Romberg sign
- Involuntary movements of the eyes (nystagmus)
- Falling towards the lesion/affected side
- Unsteadiness when walking, standing, or sitting
- Difficulty sitting or standing unsupported
- Tendency to fall backward
- Abnormal swaying with tandem gait
- Need to outstretch a foot to catch oneself from falling
- Irregular rhythm
- Irregular steps
- Truncal titubation
- Unilateral lesion
4How is Truncal Ataxia diagnosed?
The following tests of the neuro exam are done to examine the vestibulocerebellum and spinocerebellum (midline):
- Tandem gait
To test whether a suspected patient has truncal ataxia, the doctor asks the patient to sit up with arms crossed. If support is needed while the patient is sitting, then it is a sign of truncal ataxia. The stance of a patient with truncal ataxia is broad-based, is in a tandem position, and is standing on one leg, usually leaning towards the direction where the lesion is.
A Romberg test can also be done to test truncal ataxia.
- Ask the patient to stand
- Ask the patient to close his/her eyes
Negative/Normal = no change
Positive = loss of position sense
Truncal ataxia has a rating scale to measure the degree of truncal ataxia that a patient has. This was measured by independent observers. Truncal ataxia may be diagnosed through the following grades:
Truncal ataxia is measured as grade 1 if the symptoms shown by the patient is mild to moderate imbalance but he/she can walk independently. Truncal ataxia is measured as grade 2 if the symptoms shown by the patient is a severe imbalance withstanding, but he/she cannot walk without any support. Truncal ataxia is measured as grade 3 if the patient is falling at upright posture.
CT scan or MRI scan can also be used to diagnose truncal ataxia as these procedures show the abnormalities in the brain which could most likely pinpoint midline lesions in the cerebellar vermis.
5How is Truncal Ataxia treated?
There is no cure or treatment for truncal ataxia but there are treatments available to cure the underlying conditions. Once the underlying conditions are treated, the symptoms of truncal ataxia improve as well.
In some studies, transcranial magnetic stimulation helps improve truncal ataxia in spinocerebellar degeneration. In this study, experts found that an active transcranial magnetic stimulation or TMS results in a remarkable alleviation of truncal ataxia in patients with spinocerebellar degeneration. It can, therefore, be concluded that TMS over the cerebellum actually improves truncal ataxia in patients with spinocerebellar degeneration.
As for the specific treatment per underlying disorder, only the doctor can advise whether any of these treatments are appropriate for the specific medical situation. It is essential to always discuss all treatment options with the doctor before making a decision, including making an agreement in the beginning or discontinuing any treatment plan.