Neuroschistosomiasis

Neuroschistosomiasis is central nervous system infection with Schistosoma species. S. mansoni and S. haematobium cause spinal cord and conus involvement, and S. japonicum causes cerebral disease with granulomas and seizures. It affects people with freshwater exposure in endemic regions in Africa, South America, the Middle East and Asia.

Pathophysiology. Eggs reach the spinal veins through Batson plexus, or the brain by arterial embolisation. A granulomatous host response causes mass effect, oedema and necrosis.

Spinal disease: subacute lumbosacral myeloradiculopathy with back and leg pain, paraparesis, sensory loss, and urinary retention. Cerebral disease: seizures, headache, raised intracranial pressure, focal deficit and encephalopathy. Symptoms may appear weeks to months after exposure. Features of intestinal or urinary schistosomiasis may be present.

Red flags.

• Acute conus and cauda equina syndrome after freshwater exposure in an endemic area.
• Seizures with eosinophilia in a returning traveller.

MRI of the spine shows swelling of the conus and lower cord with a patchy, heterogeneous "arborised" enhancement pattern. Brain MRI shows enhancing nodules with oedema. CSF shows mild pleocytosis with eosinophils, raised protein and sometimes oligoclonal bands, with specific antibody. Serology on serum is helpful (in travellers). Stool or urine ova may be absent. Rectal or neural biopsy is rarely needed. Exclude other causes of myelitis.

Differential diagnosis.

• Transverse myelitis, neuromyelitis optica spectrum disorder and tuberculous myelitis.
• Spinal tumour, neurocysticercosis and tuberculoma.
• Lymphoma and sarcoidosis.

Treat promptly to limit permanent damage.

Corticosteroids. Prednisolone 1 mg/kg daily (maximum 60 mg) or methylprednisolone 1 g IV daily for 3 to 5 days in severe myelitis, then tapered over 4 to 6 weeks.

Praziquantel. 40 mg/kg orally as a single dose (or 60 mg/kg in three divided doses over one day), given with or just after steroids to reduce worsening of inflammation. Some regimens repeat the dose after 2 to 4 weeks.

Seizures. Levetiracetam 500 mg twice daily, increased to 1500 mg twice daily (adjust to eGFR). Avoid enzyme inducing drugs that lower praziquantel levels (carbamazepine, phenytoin).

Surgery. Decompression or biopsy for a large mass or if the diagnosis is uncertain.

Rehabilitation. Physiotherapy, bladder care (intermittent catheterisation) and spasticity treatment.

Monitoring. MRI at 3 to 6 months and neurological recovery, which is better with early treatment.

Referral and escalation. Refer to infectious diseases, tropical medicine and neurology.

Special groups. In pregnancy, praziquantel is generally considered acceptable after the first trimester, with specialist advice.