Generalized sensory neuropathies should be distinguished from subacute sensory neuronopathies, which are characterized by pain, paresthesia, and numbness in the limbs. The latter demonstrate a marked loss of proprioception and vibration, ataxia, and areflexia in an entire limb with a loss of pain and temperature to a lesser degree. The sensory loss may be more pronounced in the upper extremities than the lower extremities; therefore, it is not strictly length dependent, distinguishing it from a polyneuropathy. The differential diagnosis is Sjo gren's syndrome, paraneoplastic origin, hereditary disease, and idiopathic disease. The lesion is at the level of the dorsal root ganglion.
Dorsal root ganglion and dorsal horn lesions tend to have very similar anatomical patterns of sensory loss to radiculopathies; however, dorsal horn lesions are more likely to have dissociated loss as the dorsal root fibers separate into the medial (large myelinated) and lateral (thinly myelinated and unmyelinated) bundles as they enter the dorsal horn.
Tabes dorsalis is characterized by diminished proprioception and vibration in the legs, sensory ataxia of gait, areflexia, and aching/lancinating pains in the legs. Additionally, there may be autonomic disturbances, including bladder atony, pupillary abnormalities, and impotence. Generally there is preservation of touch, pain, and temperature sensation. Distal weakness and atrophy may be a late manifestation of tabes dorsalis attributed to extension of syphilitic process to the anterior horn cell. Pathologically, tabes dorsalis is concentrated in the dorsal roots, dorsal funiculi, and posterior columns of the lumbosacral and lower thoracic spinal cord. The dorsal root ganglion is rarely affected.
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