Certain rare polyneuropathies (amyloid, Tangier disease, and Fabry disease) that preferentially affect small fibers in the nerves of the upper extremities can reproduce the dissociated sensory loss that is characteristic of a syrinx (“pseudosyringomyelic” deficit), but motor abnormalities are not prominent in these neuropathic cases. These diseases are discussed in Chap. 43.
For cases originating in a tumor, typically ependymoma in adults, resection of the tumor and some degree of decompression of the syrinx cavity can be undertaken to prevent progression of symptoms. The cyst fluid may be high in protein and viscid (unlike the low-protein fluid of the usual syrinx).
The only therapy of lasting value for type I syringomyelia (related to Chiari malformation) is surgical decompression of the foramen magnum and upper cervical canal. Headache and neck pain are helped most; ataxia and nystagmus tend to persist, but these are related to the Chiari process. The cavity tends to at least cease enlarging. Radiation therapy, which was formerly recommended, is of no benefit. The operation advised by Gardner, of plugging the connection between the fourth ventricle and the central canal of the cervical cord, has been abandoned. There were complications of this operative procedure, and the results were no better than those obtained from simple decompression. The decompression operation also carries some risk, especially if there is an attempt to excise the tonsillar projections of the cerebellum. In the series of Logue and Edwards, comprising 56 cases of type I syringomyelia, the occipitocervical pain was relieved by decompression in most patients, but the shoulder-arm pain usually persisted. Upper motor neuron weakness of the legs and sensory ataxia were often improved, whereas the segmental sensory and motor manifestations of the syringomyelia were not. Hankinson, in the past, had reported good results from decompression in 75 percent of type I cases of syringomyelia. In the retrospective review of 141 adult patients by Stevens and colleagues, good surgical outcome was achieved in 50 percent of those with minor degrees of descent of the cerebellar tonsils, but in only 12 percent of those with major cerebellar ectopia. A distended syrinx also led to a more favorable outcome. Whether the long-term course of these diseases is altered has not been determined. Other surgical series of Chiari-syrinx are discussed and cited in Chap. 37.
Syringotomy or shunting of the cavity has been performed in type I and some of the type II (idiopathic) cases, but the results have been unpredictable. Love and Olafson, who performed this procedure in 40 patients of both types (mainly type II), stated that 30 percent had an excellent outcome. Schurch and coworkers obtained improvement of pain and motor weakness in 5 of their 7 cases by stabilization of the spine and syringotomy with placement of a T-tube within the syrinx. In a more recent and comprehensive study of 73 patients with a developmental syrinx operated by Sgouros and Williams (1995), one-half remained clinically stable for a 10-year period; 15 percent had serious complications from the surgery, however. Our experience with this procedure has not persuaded us of its lasting value; most of these patients, even those who reported some improvement originally, soon relapsed to their preoperative state, and the disease then progressed in the usual way. An enlarged cervical cord with progressive clinical worsening may nonetheless justify an attempt to shunt the cavity. Other comments are found in Chap. 37.