The clinical picture varies in the four pathologic types previously listed, the differences depending not only on the extent of the syrinx but also on the associated pathologic changes, particularly those related to the Chiari malformation. When there is no Chiari malformation, the association of syringomyelia with an intramedullary tumor (type III), particularly ependymoma, should be suspected; there is a disassociated sensorimotor abnormality extending over many segments of the body. Most cases of syrinx cavity that we have seen in adults have been from ependymoma. With von Hippel-Lindau disease, the diagnosis hinges on the finding of the characteristic hereditary hemangioblastoma in the syrinx and retinal and cerebellar vascular malformations. In posttraumatic cases, necrosis of the spinal cord that has been stable for months or years begins to cause pain and spreading sensory or motor loss, recognizable only in segments above the original lesion (Schurch et al). This occurred in approximately 3 percent of the traumatic myelopathy cases of Rossier and coworkers, more often in quadriplegics than in paraplegics. The posttraumatic syrinx is not as well defined anatomically as the usual forms of syringomyelia but consists instead of several contiguous areas of glia-lined myelomalacia with differing degrees of cavitation. In some instances of progressive spinal cord symptoms occurring several years after spinal surgery, the lesion has proved to be one of arachnoiditis and cord atrophy and not a syrinx (Avrahami et al).
In the typical type I developmental syrinx (idiopathic, Chiari-associated developmental syringomyelia), symptoms usually begin in early adult life (20 to 40 years). Males and females are equally affected. Rarely, some abnormality is noted at birth, but usually the first symptom appears in late childhood or adolescence. The onset is usually insidious and the course irregularly progressive. In many instances, the symptoms or signs are discovered accidentally, for example, as a result of painless burn or atrophy of the hand, and the patient cannot say when the disease began. Rarely, there is an almost apoplectic onset or worsening; there are cases on record of an aggravation of old symptoms or the appearance of new symptoms after a violent strain or paroxysm of coughing. Trauma is a less certain precipitant. Once the disease is recognized, some patients remain much the same for years, even decades, but more often there is intermittent progression to the point of being chair-bound within 5 to 20 years. This extremely variable course makes it difficult to evaluate therapy.
The precise clinical picture at any given point in the evolution of the disease depends on the cross-sectional and longitudinal extent of the syrinx, but certain clinical features are so common that the diagnosis can hardly be made without them. These traditionally cited elements are (1) segmental weakness and atrophy of the hands and arms, (2) loss of some or all tendon reflexes in the arms, and (3) segmental anesthesia of a dissociated type (loss of pain and thermal sense and preservation of the sense of touch) over the neck, shoulders, and arms. The last of these leads to one of the most characteristic features of syringomyelia: painless injuries and burns of the hands. Finally, there are in cases of extensive cavitation weakness and ataxia of the legs from involvement of the corticospinal tracts (possibly at their decussation) and posterior columns in the cervical region.
Kyphoscoliosis is added in many of the cases and in nearly one-quarter of them there is an overt cervicooccipital malformation (short neck, low hairline, odd posture of the head and neck, fused or missing cervical vertebrae, that is, Klippel-Feil abnormality).