Chronic CNS Infection

In chronic schistosomiasis, there may be cerebral or spinal involvement, often in young patients. It is possible that CNS involvement has been underdiagnosed and is now becoming more readily recognized with CT or MR scanning.

Infection of the brain presents clinically with a wide spectrum of signs and symptoms: headache, nausea, vertigo, visual and speech defects, rigidity, spasm, mental confusion, and hemiplegia have all been reported. The most common immediate diagnosis will be of a cerebral hemorrhage or brain tumor (a subarachnoid hemorrhage has occurred in at least one patient). CT and MR have shown multifocal and localized defects. T 1-weighted MRI shows edema; T 2-weighted and proton-density MR have shown nodular masses, sometimes iso-intense and surrounded by edema. Following specific treatment, scans return to normal and the clinical symptoms disappear.

In very chronic schistosomiasis mansoni, cerebral atrophy has been reported (Fig. 2.67). Ultrasonography has shown a reduced brain mantle and dilated ventricles, confirmed by CT. In one series 36% of patients showed cortical atrophy and 12% showed central atrophy. Autopsy has confirmed multiple small granulomas in the cortex and gliosis after healing. Some patients have massive granulomas and blockage of several vessels by eggs.

When the spinal cord is infected, the patient complains of low back pain and progressive CNS impairment, which may include paraplegia and urinary symptoms (Figs. 2.65, 2.66). Schistosomiasis causes localized granulomas or arachnoiditis or, in some cases, transverse myelitis. There is usually swelling of the cord, sometimes with an intramedullary mass. The transverse myelitis is probably due to vascular thrombosis, and when this occurs the response to treatment is poor. In other patients, the paraplegia and other effects may resolve completely with specific treatment, though treatment is not always successful. Computed tomography and MRI have confirmed the swelling of the cord, which can be nodular or confluent and is usually enhanced with gadolinium. This is best seen on T 1-weighted MR scanning, while on T 2-weighted MR images the swollen cord or conus medullaris appears inhomogeneous with a high signal intensity (Fig. 2.66). Intraoperative sonography has shown a hyperechoic mass.

CT myelography can also demonstrate conus or cauda equina expansion and improvement after treatment (Figs. 2.65, 2.66). Irregularity and matting of the nerve roots may also be seen. In patients with myelitis (in some series, nearly half the patients) the myelogram may be normal.

If scanning is not available, contrast myelography will demonstrate obstruction or displacement of the cord but in some patients it will be normal in spite of the clinical symptoms.

The differential diagnosis can be extremely difficult, particularly in young patients with epilepsy or progressive paraplegia. Infections, such as tuberculosis or syphilis, must be excluded. Wherever schistosomiasis is endemic, the onset of these CNS symptoms, particularly if slow and otherwise unexplained, or the sudden onset of epilepsy in a teenager, should suggest the possibility of schistosomiasis: it is probably more common than usually thought.

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Fig. 2.67 A-I. Cerebral schistosomiasis: cerebral atrophy following chronic schistosomiasis mansoni. CT scans of three Egyptian men who all had liver fibrosis, ascites, and splenomegaly. A-C Patient aged 35 years, with wide sulci and fissures including of the cerebellum. The ventricular system was normal. Assessed as mild cortical atrophy; sulci=3 mm. D-F Patient aged 42 years with prominent cortical sulci and a normal ventricular system. This case was assessed as moderate cortical atrophy and mild cerebral atrophy; sulci=4 mm. G-I Patient aged 17 years who had undergone splenectomy and had cor pulmonale. Prominent sulci; normal ventricular system. This case was assessed as moderate cortical atrophy and mild cerebral atrophy. Sulci=4 mm. All three patients clinically showed apathy, resignation, lack of activity, lack of curiosity, and a prolonged response time to simple questions. (Courtesy of Dr. H.H. Khalil and colleagues; scan in B and C courtesy of Am J Trop Med Hyg, 1986).