Widespread disease of the sensory (dorsal root) ganglia produces many of the same sensory defects as disease of the posterior nerve roots (see below under “Tabetic Syndrome”), but it has greater hypesthesia and hypalgesia of proximal areas of the body such as the face, oral mucosa, scalp, trunk, and genitalia. Proprioception is diminished or lost in distal and, to a variable extent, proximal body parts, and occurs in parallel with ataxic movements, often quite severe, and with pseudoathetosis. These latter features, perhaps more than any others, are characteristic of a ganglionopathy and may render the patient incapable of using the limbs, despite preserved strength. Tendon reflexes are lost. Sometimes there are additional features of dysautonomia, but strength is entirely spared. Recognition of this unusual pattern of pansensory loss is of considerable diagnostic importance, because it raises for consideration a number of underlying diseases that might otherwise be overlooked; these diseases are discussed in Chap. 43. The main causes of this syndrome are paraneoplastic, connective tissue disease, particularly Sjögren syndrome, toxic exposure, and idiopathic inflammation.
Tabetic Syndrome (See Table 8-3 and Fig. 8-7)
The tabetic syndrome, characterized by tabes dorsalis, consists of sensory ataxia and severe imbalance with a positive Romberg test as a result of proprioceptive loss. In its most extreme form the feet slap and stomp as they meet the ground. It can be considered a subtype of polyradiculopathy or ganglionopathy but it also classified with diseases of the spinal cord because the same disorder derives from diseases that affect the posterior columns. Furthermore, the processes that affect that root or ganglion lead to wallerian degeneration of posterior columns. Although inextricably allied in the past with neurosyphilis, it occurs in diabetes mellitus and other diseases that involve the posterior roots or dorsal root ganglia, such as paraneoplastic ganglionopathies.
In addition to the sensory ataxia, numbness or paresthesia and “lightning” or lancinating pains are frequent complaints; areflexia, and hypotonia without significant muscle weakness is found. The sensory loss may involve only vibration and position senses in the lower extremities but loss or impairment of superficial or deep pain sense or of touch may appear in severe cases. Loss of deep tendon reflexes distinguishes the sensory root syndrome from a lesion in the posterior columns. The feet and legs are most affected in tabes, much less often the arms and trunk. The Romberg sign is prominent, as noted earlier. In extreme cases, atonicity of the bladder with retention of urine and trophic joint changes (Charcot joints) and crises of abdominal (“gastric”) pains are associated.
Cases of congenital absence of all cutaneous sensation resulting from the lack of development of small sensory ganglion cells may produce the tabetic syndrome; this is discussed in Chap. 7. A similar but partial defect may be found in the Riley-Day syndrome (Chap. 25). There are also forms of hereditary polyneuropathy that cause universal insensitivity.
(See Also Chap. 42.)
Complete Spinal Sensory Syndrome (Fig. 8-7)
With a complete transverse disruption of the spinal cord, the most striking features are paralysis and loss of all forms of sensation below a level that corresponds to the lesion. There may be a narrow zone of hyperesthesia at the upper margin of the anesthetic zone. Loss of pain, temperature, and touch sensation may begin one or two segments below the level of the lesion; vibratory and position senses have less-discrete levels but they can be detected by careful examination. The sensory (and motor) loss in spinal cord lesions that involve both gray and white matter is expressed in patterns corresponding to bodily segments or dermatomes. These are shown in Figs. 8-3 and 8-4 and are most obvious on the trunk, where each intercostal nerve has a transverse distribution.