Introduction
Neurocysticercosis is an infection of the central nervous system with the larval forms (cysticerci) of the pork tapeworm Taenia solium1. T solium infection is acquired through the consumption of raw or poorly cooked pork containing the cysticerci, which then develop into an adult worm inhabiting the human intestine. Humans can also be infected by external autoinfection via the faecal oral route by ingesting taenia eggs shed in the faeces of a human carrier of the tapeworm2. Internal autoinfection may also occur but this is less likely because the eggs have to pass through a period of peptic digestion before they can invade human tissue3.

Between 5 and 40% of adult carriers of T solium develop cysticercosis here the cysticerci are scattered throughout the body4. When present in the central nervous system the cysticerci can cause seizures, hydrocephalus and other neurological disorders5. We report a case of a young male patient, originally from Guatemala, who presented with a witnessed tonic-clonic seizure secondary to neurocysticercosis.

Case Report
A 25 year old previously healthy male presented to the Accident and Emergency department following a witnessed generalized tonic-clonic seizure. He was originally from Guatemala, living in Ireland for two years. He was a non-drinker, had a family history of epilepsy secondary to neurocysticercosis but he had no previous history of seizures.

On examination, following spontaneous resolution of the seizure, he was apyrexial, vital signs normal and he had an abrasion over his left eye. He was orientated in time, place and person. Central and peripheral neurological examination was normal. Investigations revealed normal white cell count of 9.1 (3.5 – 11.0), eosinophils of 0.1 (0 – 0.5), plasma sodium of 138 mmol/l (135 – 145 mmol/l), calcium of 2.38 mmol/l (2.2 – 2.6 mmol/l), random blood glucose of 4.6 mmol/l (4.0 – 6.0 mmol/l). Erthyrocyte sedimentation rate of 11 mm/hr (0 – 10 mm/hr), C-reactive protein of < 3.67 mg/l (0 – 4 mg/l). Stool culture was negative for parasites. Early morning urine specimens for acid fast bacilli and culture for tuberculous disease were negative. Mantoux test was negative. Serology for toxoplasmosis, cryptococcosis, syphilis and HIV infection was negative. Lumbar puncture demonstrated a white cell count <1, protein = 0.18 g/l (0.15 – 0.40 g/l), glucose = 3.5 mmol/l with a paired blood glucose of 4.4 mmol/l. ZN stain for acid fast bacilli, India ink stain and cryptoccocal antigen in the cerebrospinal fluid were negative. Serology for T. solium in plasma and cerebrospinal fluid was negative.

CT scan of the brain with contrast showed 2 areas of calcification in the Right and Left parietal lobes and a wedge shaped area of low attenuation within the Left parietal lobe with associated oedema (Figure 1). MRI brain identified a high signal intensity 4cm lesion in the left parietal lobe with a small ring enhancing central focus (Figure 2). Plain X-rays of the humerus, femur and tibia showed no areas of calcification within the soft tissue. Chest X-ray was normal.

On the basis of the epidemiological history, the exclusion of other potential granulomatous disease, the clinical and radiological findings as described above, the patient was diagnosed with presumptive neurocysticercosis. He was treated with an eight-day course of oral albendazole (400mg twice daily) in conjunction with 40 mg of oral prednisolone for 5 days. To prevent seizure recurrence he was commenced on sodium valproate. He was discharged well and on follow up has had no further seizures.

Neurocysticercosis is the most frequent parasitic disease of the human nervous system and in the developing world is the commonest cause of late onset epilepsy1. This however is the first reported case of neurocysticercosis presenting within the Irish healthcare system.

Cysticercosis is endemic in rural areas of Latin America, Asia, Africa and places where undercooked pork is consumed regularly6. Women are more likely to be infected than men, the rate of infection increasesd until the end of the fourth decade and declines thereafter.6 Cysticercosis can affect the subcutaneous tissues, intermuscular fascia, muscles and other organs forming cystic nodules under the skin, in the mouth, breast, sexual organs, heart and muscle. In neurocysticercosis, the larva of T. solium enters the brain tissue through the bloodstream. Once in the brain the larva grow slowly, taking several months to evolve into a cysticercus, which may eventually reach a diameter of greater than 3cm in size7. Once fully grown the cysticercus lies dormant. The incubation period varies from a few months to 30 years, but most patients develop neurological symptoms within seven years. The parasite causes inflammation within the brain, the severity of which depends on the degree of the host’s immune response, which can lead to displacement of neural structures, oedema, arachnoiditis and reactive astrogliosis7. The most frequent symptom of neurocysticercosis is seizure although patients may present with headaches, features of increased intracranial pressure, cranial nerve palsies and hydrocephalus7. Epilepsy can arise from the cysticercus containing the live parasite or from a granuloma in which the cysticerci have been destroyed by the host’s own immune response.

Diagnosis of neurocysticercosis on clinical grounds is difficult, because signs and symptoms are non-specific. The gold standard of diagnosis is pathological confirmation with biopsy or autopsy, which has obvious limitations. Therefore diagnosis is based on a combination of the epidemiological history of exposure to the T. solium parasite, the presence of subcutaneous nodules, the radiological findings on CT and MRI imaging of the brain and exclusion of other potential granulomatous brain disease in particular tuberculosis, toxoplasmosis and HIV infection.

Laboratory tests are not usually helpful. Enzyme linked immunosorbent assay (ELISA) and enzyme linked immunoelectrotransfer blot (EITB) are available to detect antibodies that indicate present or past infection. The ELISA test however has high false positive and false negative rates with a sensitivity of 50% and a specificity of 65% for neurocysticercosis8. The EITB test appears to be more sensitive and specific than ELISA for the diagnosis of human cysticercosis but in patients with neurocysticercosis the sensitivity may be as low as 25%9. Antibody based tests are also limited by the fact that they may indicate only previous exposure to infection with the parasite and not necessarily current infection. To overcome this problem antigen detection assays and PCR assays are under evaluation and may in the future contribute to the diagnosis of current infection with cysticercosis.

Treatment of neurocysticercosis is controversial, this is partly due to a lack of appropriate randomized clinical trials. Short courses of the antiparasitic drugs albendazole and praziquantel effectively destroy the cerebral parenchymal cystic lesions, with remission or marked improvement in the associated seizure disorder10,11. Opponents of anticysticercal treatment however argue that even if the cysticercal lesions are left untreated, they either disappear spontaneously or calcify and doubts have been expressed whether antiparasitic therapy has a positive effect on seizure control12. Anticysticercal treatment is also potentially hazardous given that, destruction of the parasite may initiate an acute inflammatory response and aggravate hydrocephalus or cerebral oedema13. To counteract this event concomitant corticosteroids should be administered at a dose similar to that used in our patient14. Two randomized, placebo-controlled, double blind clinical trials are under way in Ecuador and Peru to assess whether albendazole added to symptomatic treatment influences resolution of lesions and long-term clinical outcome. Certainly in our patient treatment with albendazole appeared to be effective with near complete resolution of the cerebral lesion and no further seizure activity.

References

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