Giant primary cerebral hydatid cyst: A rare cause of childhood seizure.

We report a 9-year-old girl who presented with focal seizures, hemiparesis, headache, vomiting and bilateral optic atrophy. CT scan revealed a giant solitary cyst in the left parietal lobe. Serology and histopathology of the excised cyst confirmed the diagnosis of neurohydatidosis which is a rare cause of childhood seizure.

Introduction

Hydatid disease is endemic in the Middle-East, Mediterranean countries, South America, North Africa and Australia.[1] Intracranial hydatid cysts account for 0.5-3% of all the cases of hydatid disease in humans.[2] They contribute to 1-2% of all the intracranial space occupying lesions (ICSOL).[3] The incidence of neurohydatidosis as reported in India is still lesser, i.e., 0.2%.[4] Here we report a case of giant primary intracranial hydatid cyst arising from the left parietal lobe, causing midline shift and compression of the contralateral ventricle.

Case Report

A 9-year-old female presented with right-sided partial seizures, decreased vision in both eyes, headache, vomiting, fever for 15 days and right sided hemiparesis for last 2 days. On examination child was conscious, oriented, and hemodynamicaly stable. Higher mental functions were normal. The child had nystagmus in both eyes with fast component towards left. Fundus examination revealed bilateral optic atrophy. She also had right-sided upper motor neuron facial palsy. There were no meningeal or cerebellar signs. Rest of the systemic examination did not reveal any abnormality. Chest radiography and abdominal sonography were normal. Neuroimaging revealed a giant solitary cyst in the left parietal lobe measuring 9 × 7 × 6 cm in size, involving almost whole of the parietal lobe, causing midline shift and compression of the contralateral ventricle [Figure 1]. Serum Echinococcus ELISA was done which was 0.96 D (positive ≥0.3 D). Total excision of the cyst was done and post-operative recovery was uneventful. The histopathology of the excised cyst revealed dead scolices of E. granulosus which further confirmed the diagnosis.

Figure 1

CT brain showing a giant solitary cyst measuring 9 × 7 × 6 cm in left parietal lobe causing a midline shift

Discussion

Echinococcosis or hydatidosis occurs in two predominant clinical forms. Cystic hydatid disease caused by Echinococcus granulosus is characterized by slowly progressive cystic lesions surrounded by a tough, fibrous capsule. The other form which is relatively less prevalent is the alveolar hydatid disease, characterized by multiple ill-defined cystic lesions which may resemble malignancy and are associated with poorer prognosis.[5]

Echinococcus is a cestode whose larval stage is responsible for causing hydatid disease in humans. The definitive hosts are dog and fox; and the intermediate hosts are sheep, goat and cattle. History of direct contact with dogs is not available in all the cases, as infection can be acquired by eating food and milk contaminated with eggs of this tapeworm. Oncospheres released from eggs in the intestine enter the portal circulation and majority localize after getting “filtered” within the liver which is the most common affected site followed by lungs. The other organs which may be affected are bone, genitourinary system, bowels and subcutaneous tissue.[5] Intracranial hydatid disease is extremely uncommon. A majority of intracranial hydatid cysts are located in the supratentorial compartment with the most common location being middle cerebral artery territory in the parietal lobe as seen in the present case.[6] The other less commonly reported sites are skull, cavernous sinus, eye ball, pons, skull, extradural, cerebellum and ventricles.[7]

Cerebral hydatid disease is seen more commonly in the pediatric population. Intracranial hydatid cysts grow slowly with a growth rate reported to be ranging from 1.5 cm/year to 10 cm/year.[67] It generally presents late especially in the pediatric population due to open sutures, elasticity of skull bones and relative compressibility of neural tissue.[8] The common presenting features of neurohydatidosis are features of raised intracranial pressure, focal neurological deficits, hydrocephalus, papilledema and loss of vision.[7] This case presented with seizures which is a rare manifestation of neurohydatidosis.[2]

Intracranial hydatid cysts are classified as primary and secondary depending on origin, structure and fertility.[79] Primary cysts which are more common, arise from direct invasion of the larvae which manage to cross liver and lungs and reach brain without affecting other organs. They are generally solitary but may be multiple with each cyst having a separate pericyst with brood capsules and scolices. Each primary cyst arises from separate larvae reaching brain. Rupture of the primary cyst can result in recurrence as they are fertile. Secondary cysts are generally multiple as they develop after rupture of a primary cyst in some other organ leading to embolization of brood capsules to brain. These are generally infertile as they lack brood capsules and scolices. The present case did not reveal involvement of any other organ hence it was primary and this was further confirmed by histopathology.

The diagnosis of neurohydatidosis is established by neuroimaging which reveals a well-defined solitary, non-enhancing, spherical, cystic lesion that is iso-dense/iso-intense with CSF in the middle cerebral artery territory without surrounding edema. The presence of significant edema indicates some complication like rupture or secondary infection. Such cases may be difficult to differentiate from other pathologies like abscess, astrocytoma, large granulomas and cystic granulomas.[6] Other differentials which should be considered based on the radiological appearance are arachnoid cyst, epidermoid cyst, cystic glial tumors, paraventricular ependymal cyst, lateral ventricular cyst and porencephalic cyst.[9] MRI is considered as a better imaging modality than CT as it helps in better anatomical delineation that aids in meticulous surgical planning.[9] MRI could not be done in the present case due to non-affordability. Serological tests like ELISA are supportive of the diagnosis and have a sensitivity of 85%.[2] Confirmatory diagnosis can only be made by histopathological evaluation of the excised cyst like in the present case.

The definitive management of a cerebral hydatid cyst is surgical removal of the entire cyst without rupture preferably by a pericystic hydraulic method (Dowling-Orlando technique). Inadvertent rupture of a cyst per-operatively may result in complications like fatal anaphylactic reaction, recurrence, infections like meningitis or brain abscess. Chemotherapy using albendazole alone or in combination with praziquintal may be administered post-operatively for 3-6 months. Chemotherapy alone may be used in patients who are not eligible for surgery or in the case of recurrence, but is not an efficacious modality of treatment in a primary hydatid cyst of brain.[237]

To conclude neurohydatidosis though uncommon should be kept as a possibility in cases presenting with seizures. They should be meticulously investigated and appropriately managed to improve the outcome.