The clinical syndrome consists of a progressive painless loss of motor and then sensory function, usually with sphincter disorder, over weeks. Imaging studies demonstrate an area of T2 signal change in the cord, occupying one or several contiguous segments, similar to neuromyelitis optica (Devic disease); some have slight enhancement with gadolinium or rarely, imaging may be normal. This is in distinction to the nodular enhancing appearance of an intramedullary metastasis or of extradural metastatic disease with cord compression.
The CSF may contain a few mononuclear cells and a slightly increased protein, or it may be normal. The lesions are essentially of necrotic type and respect neither gray nor white matter, but the latter is more affected. There is little or no evidence of an infective-inflammatory or ischemic lesion, for the blood vessels, apart from a modest cuffing with mononuclear cells are normal. No tumor cells are visible in the CSF, meninges, or spinal cord tissue, and no virus has been isolated. Unlike the situation in most of the paraneoplastic neurologic disorders, there are no diagnostic markers by way of specific antineural antibodies. In particular, this myelopathy does not seem to be a component of the anti-Hu–associated encephalitis-neuropathy spectrum.
In some cases of paraneoplastic myelopathy, the pathologic changes have been more chronic, confined to the posterior and lateral columns, and associated with a diffuse loss of cerebellar Purkinje cells. This latter syndrome may have a special association with ovarian carcinoma but has been observed with carcinoma of other types and with Hodgkin disease as discussed in Chap. 30. Most of the reported cases of these types have ended fatally. Steroids and plasma exchanges have been of no clear value. Treatment of the underlying systemic tumor or immunosuppression has also failed in most cases to alter the myelopathy according to Flanagan and colleagues (2011). A rare variety of anterior horn cell destruction that resembles motor neuron diseases is known to occur with certain lymphomas; it is also discussed with the paraneoplastic syndromes in Chap. 30.
Two distinct entities seem to be encompassed under this name, both rare; a progressive myelopathy and a regional disorder, mainly of the abdominal muscles. Whitely and colleagues drew attention to the process characterized clinically by tonic rigidity and intermittent myoclonic jerking of the trunk and limb muscles and by painful spasms of these muscles evoked by sensory or emotional stimuli. Their cases were progressive and eventually involved the limbs.
In the few well-studied cases of this type, the brunt of the pathologic process has fallen on the cervical portion of the spinal cord. Widespread loss of internuncial neurons with relative sparing of the anterior horn cells, reactive gliosis and microglial proliferation, conspicuous lymphocytic cuffing of small blood vessels, and scanty meningeal inflammation have been the main findings. Involvement of the white matter is less marked. The pathophysiology of the rigidity in these cases is presumed to be because of the impaired function (or destruction) of Renshaw cells, with the release of tonic reflexes (Penry et al). The painful spasms and dysesthesias relate in some way to neuronal lesions in the posterior horns of the spinal cord and dorsal root ganglia. Whitely and Lhermitte and their coworkers proposed that these cases probably represent an obscure form of viral myelitis.