CASE HISTORY

A male child, aged 10 years old, presented to us in our neurosurgical clinic. One year previous he had headache with unsteady gait and disturbed manual motor act. There was no history of trauma, infection, previous surgery or systemic illness. On examination, he had disturbed motor co-ordination in both upper and lower extremities, more so on the left side, with r"arked central ataxia. His weight was 36 kg. The Initial Study by brain MRI with contrast enhancement revealed a lesion (about 29x24x21 mm in its maximum dimension) in the left cerebellum (Fig. I and Fig. 2).

	Figure 1 — Saggital post-contrast T1-weighted image of brain MRl reveals the enhancement of the lestion by contrast injection with the surrounding low signal area of thr perilesional oedema.

The lesion extended to the left side of the pons, cerebellar peduncle, effacing and displacing the fourth ventricle, causing supratentorial ventricular dilatation. There was intense enhancement after contrast injection. On laboratory investigation he had double high positive result of IgE and IgG for toxoplasmosis (> 2500 un/ml) in his serum. There were negative IgG specific antibodies for toxoplasmosis in his mother's serum. Both the child and his mother were free as regard HIV antibodies in their serum. We started specific treatment for toxoplasmosis including pyrimethamine, sulfadiazine, spiromycin and corticosteroid for the oedema. All the medication were adjusted according to the body weight. One month later, the patient markedly unproved, both clinically and serologically, by starting to drop IgG for toxoplastnosis (< 950 u/ml) in his serum. There was a reduction in the size of the lesion (21x15x11 mm in its maximum dimension) on follow up MRI brain with resolving of the perifocal oedema (Fig. 3).

Figure 2 (a) and (b) T1-weighted image of A) axial, B) coronal post-contrast brain MRI reveals the lesion in the left cerebellum, it's extend, intense enhancement, perilesional oedema and effaced and displaced fourth ventricle.

Figure 3 (a) and (b) T1- weighted image of A) axial, B) coronal post-contrast follow up brain MRI after specific treatment reveals regression in lesion size, oedema and restoring of the fourth ventricle patency.

DISCUSSION

Toxoplasmosis is a common infection with increasing incidence in AIDS patients and in other immunocompromised conditions.(1,8) In immunocompromised patients, neurotoxoplasmosis was considered if the patients have signs of focal neurological impairment and a positive response to the serum test for toxoplasma gondii. The diagnosis is then confirmed by clinical and neuroradiological improvement (especially brain MRI scan) after starting specific therapy for the disease. (1,3,11) In immunocompetent patients the postnatally acquired toxoplasmosis is usually a mild or a symptomatic disease and manifestations related to the central nervous system are very rare. (2,5,12)

A positive focal neurotoxoplasmosis is usually demonstrated in T2-weighted image of the brain MRI scan. A few reports discuss the value of T1-weighted image with contrast enhancement of brain MRI scan of predictive value as well as prognostic measure for the diagnosis and accurate follow up for neurotoxoplasmosis under specific treatment.(12,13) Other reports discussing the predominant location of focal acquired neurotoxoplasmosis in immunocompetent cases suggest the basal ganalia, thalami, and cerebral hemispheres. The posterior fossa lesions were not studied. (12,13,14)

Our patient presented with a lesion in the cerebellar tissue without evidence of immunosuppressive disorders. We excluded the possibility of congenital toxoplasmosis by examination of his mother's serum for the presence of specific antibodies against toxoplasma gondii. Use of MRI scan as successful neurodiagnostic tool (especially for T1 weighted image) for detection and follow up of intracranial toxoplasmosis is highly recommended. (1,11,14)

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