From the Guidelines
A person with an intact spinocerebellar tract but impaired dorsal column medial lemniscal pathway would primarily manifest with sensory deficits, including decreased or absent vibration sense and proprioception, leading to sensory ataxia, as noted in the 2024 study on dizziness and ataxia 1. This manifestation would result in difficulty knowing where their limbs are in space without visual input, leading to an unsteady gait that worsens when their eyes are closed, characterized by a positive Romberg sign. Key features of this condition include:
- Decreased or absent vibration sense and proprioception (position sense) in the affected limbs
- Impaired two-point discrimination, stereognosis (ability to identify objects by touch), and graphesthesia (ability to identify numbers/letters traced on skin)
- Diminished fine touch and pressure sensation
- Intact pain and temperature sensation, as these are carried by the spinothalamic tract
- Preservation of coordination of movements and muscle tone regulation due to the intact spinocerebellar tract, without signs of cerebellar ataxia such as intention tremor, dysmetria, or dysdiadochokinesia, as discussed in the context of spinocerebellar ataxias and sensory neuropathies 1. The clinical evaluation and diagnostic approach for such patients would involve assessing these sensory and motor functions, potentially including electrodiagnostic testing and targeted imaging to evaluate the extent of the impairment, as suggested by the study on the appropriateness criteria for dizziness and ataxia 1.
From the Research
Clinical Manifestation
The manifestation of a person with an intact spinocerebellar tract but impaired dorsal column medial lemniscal pathway would include:
- Loss of soft touch sensation
- Impaired vibratory sense
- Decreased proprioception (sense of body position and movement)
- Impaired two-point discrimination (ability to distinguish two nearby points of contact)
- Positive Romberg test (difficulty maintaining balance with eyes closed) 2
- Possible neuropathic pain after spinal cord injury, associated with decreased function in the dorsal column medial lemniscus-mediated pathway 3
Sensory Deficits
The impaired dorsal column medial lemniscal pathway would result in sensory deficits, including:
- Decreased sensitivity to vibration
- Impaired sense of pressure and joint position
- Decreased ability to discriminate between different sensations (e.g., touch, pressure, vibration) 2, 3
Proprioception and Motor Function
The spinocerebellar tract is involved in motor coordination and proprioception. However, the impaired dorsal column medial lemniscal pathway would affect proprioception, leading to:
- Impaired motor function, particularly in tasks that require precise movement and coordination
- Decreased ability to sense the position and movement of the body
- Possible difficulties with balance and posture 4