Dissociated Sensory Loss

Dissociated Sensory Loss

Dissociated sensory loss refers to impairment of selected sensory modalities with preservation, or sparing, of others. It is usually an indication of an intramedullary spinal cord lesion. For example, a focal central cord pathology. such as syringomyelia, will in the early stages selectively involve decussating fibers of the spinothalamic pathway within the ventral commissure, thus impairing pain and temperature sensation (often in a suspended, "cape-like", "bathing suit", "vest-like" or cuirasse distribution), while the dorsal columns are spared, leaving proprioception intact. The anterior spinal artery syndrome also leaves the dorsal columns intact. Conversely, pathologies confined, largely or exclusively, to the dorsal columns (classically tabes dorsalis and subacute combined degeneration of the cord from vitamin B12 deficiency, but probably most commonly seen with compressive cervical myelopathy) impair proprioception, sometimes sufficient to produce pseudoathetosis or sensory ataxia, while pain and temperature sensation is preserved. A double dissociation of sensory modalities on opposite sides of the trunk is seen in the Brown-Séquard syndrome.

Small fibre peripheral neuropathies may selective affect the fibers which transmit pain and temperature sensation, leading to a glove-and-stocking impairment to these modalities. Neuropathic (Charcot) joints and skin ulceration may occur in this situation; tendon reflexes may be preserved.

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