Classification principle
The division of ataxia into various types is based exclusively on topical diagnosis. This means that the type of disorder directly depends on the exact level at which the nervous tissue is damaged. Clinical, laboratory, or instrumental diagnostics in this context take a backseat to the topical principle, which allows for precisely correlating the site of injury with a specific type of pathology.
Sensory (posterior column) ataxia
This type of ataxia develops when structures responsible for conducting sensory information are damaged. Topically, the lesion may be localized at several levels of the nervous system:
- Peripheral level: damage to peripheral nerves.
- Spinal level: involvement of the posterior spinal roots, as well as the posterior columns (posterior funiculi).
- Cerebral level: involvement of the optic thalamus (thalamus) in the pathological process.
Cerebellar and vestibular ataxia
Cerebellar ataxia Develops with direct damage to the structures of the cerebellar system. Key lesion locations for this form include:
- The cerebellar tissue itself.
- Cerebellar pathways connecting it to other parts of the nervous system.
Vestibular ataxia This type of coordination disorder is associated with pathology of structures responsible for spatial balance. Topical diagnosis points to the following affected zones:
- Brainstem.
- The area of the IV cerebral ventricle.
Cortical ataxia
Occurs when the cerebral cortex is involved. Unlike other forms, the lesion here is localized at the highest level of the central nervous system. The following typical localization zones are distinguished:
- Frontal cortex.
- Occipitotemporal region (can occur both in isolation and combined with frontal damage).
Briefly: answers to topical questions
How to differentiate sensory ataxia from cerebellar ataxia based on clinical symptoms?
Sensory ataxia can be distinguished from cerebellar ataxia by its dependence on visual control and the presence of specific symptoms.
| Clinical sign | Sensory ataxia | Cerebellar ataxia |
|---|---|---|
| Visual control | Coordination significantly depends on vision | Depends to a lesser extent |
| Closed-eyes sign | Ataxia increases sharply, the patient loses balance | No such sharp deterioration |
| Intention tremor | Absent | Present |
| Dysarthria | Absent | Present |
| Nystagmus | Absent | Present |
Additionally, sensory ataxia presents with a characteristic "stamping" gait accompanied by a loud slapping step sound.
Specifically, which pathways in the posterior columns of the spinal cord are affected in sensory ataxia?
In sensory ataxia with lesions of the posterior columns of the spinal cord, the proprioceptive pathways—the fasciculus gracilis and fasciculus cuneatus—are affected.
In the posterior funiculi of the spinal cord, these are:
- gracilis fasciculus (fasciculus gracilis) — the medial conducting bundle;
- cuneate fasciculus (fasciculus cuneatus) — the lateral conducting bundle.
The posterior funiculi conduct impulses primarily from proprioceptors and skin receptors.
Which clinical tests are used for the differential diagnosis of vestibular ataxia?
Balance assessment and coordination tests are used for the differential diagnosis of vestibular ataxia.
Main differential sign: in vestibular ataxia, unlike cerebellar and sensory ataxia, coordination tests in the limbs are not impaired.
The following are used:
- Romberg's test — to assess balance impairment in a standing position;
- balance assessment in a sitting position;
- limb coordination tests: diadochokinesia tests, finger-to-nose test, heel-knee test;
- specific tests and studies listed in the guidelines: Dix-Hallpike test, positional tests, caloric test.
The 4 types of ataxia by topography can be remembered using the mnemonic SCVT: Sensory, Cerebellar, Vestibular, Cortical.
Class and exam questions
What principle is the classification of ataxias based on?
The classification is based exclusively on the topical diagnosis of nervous tissue damage.
Which spinal cord structures are affected in sensory ataxia?
In the sensory form, the posterior roots and posterior columns (funiculi) of the spinal cord are affected.
Where is the lesion located in the vestibular form?
The lesion is localized in the brainstem and the IV ventricle area.
What else to study on this topic
- Anatomy and functions of the posterior columns of the spinal cord
- Cerebellar pathways: afferent and efferent connections
- The role of the frontal cortex in the regulation of complex movements
- Connection of the brainstem nuclei with the fourth ventricle
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