Mystery presentation
A 5-y-old child presented to the emergency department with altered consciousness and seizures. He came from a rural area of Tunisia and had no particular antecedents. He had a history of headaches and decreased visual acuity starting 2 mo previously. On physical examination, blood pressure was 100/50 mm Hg, heart rate was 100 beats·min-1, respiratory rate was 18 breaths·min-1, and he did not have any signs of respiratory distress. His Glasgow Coma Scale score was 12 (E3V4M5). He had left-sided hemiparesis. However, he did not have any history of nausea, vomiting, or fever. Fundoscopy revealed bilateral frank papilledema. Computed tomography (CT) scan of the brain showed a large hypodense lesion surrounded by a very large area of edema. Mass effect was present, affecting the ventricular system and the medial structures, with cingulate herniation. The lesion did not enhance with contrast (Figure 1).
Computed tomography scan of the brain showing a large right frontoparietal hypodense cystic lesion surrounded by a very large area of edema.
Diagnosis
In this case, CT scan of the brain showed a large cystic right frontoparietal lesion surrounded by a very large area of edema. We suspected a hydatid cyst for many reasons—the age of child, the rural living situation in an endemic area, and the appearance of the lesion on CT scan. Differential diagnosis included neurocysticercosisis, but because of diet, this does not exist in Tunisia. However, other causes of intracerebral mass lesions such as brain tumor or congenital cyst could not be eliminated. A magnetic resonance imaging scan would have provided comprehensive information for advanced diagnosis but was unavailable for emergency use in our hospital center. Hydatid serology was also unavailable in the emergency department.
Craniotomy was performed under general anesthesia. We discovered an intra-axial cystic lesion with a thick membrane, suggesting a hydatid cyst. The cyst was completely evacuated and removed in toto without rupture to prevent recurrence or an anaphylactic reaction. Hypertonic saline was injected into the residual cavity. Histological examination revealed a hydatid cyst wall with laminated basophilic material and inflammatory cells but did not demonstrate protoscolices (parasite larvae). Abdominal ultrasound and chest radiograph did not demonstrate other cysts. Hydatic serology (enzyme-linked immunosorbent assay) was positive. The patient was treated with albendazole for 6 wk. The final outcome was excellent without neurological sequelae. Level of consciousness and vision returned to normal. Left hemiparesis and papilledema resolved. At 3-mo follow-up the patient showed no signs of recurrence and had no further seizures.
Discussion
A hydatid cyst is the larval stage of a small tapeworm, Echinococcusgranulosus. 1 The definitive hosts of echinococcus are various carnivores, most commonly dogs. Humans are accidental hosts who become infected via the fecal−oral route by ingestion of food or milk contaminated by dog feces that contain ova of the parasite or by direct contact with dogs. 1
After digestion of the embryonated egg, the oncosphere (tapeworm embryo) hatches in the intestinal track and penetrates the intestinal wall. It then spreads through the portal circulation from which it can reach the liver (60%) or the lung (25%), developing hydatid cysts in those locations. Even after pulmonary filtration, a few cysts can reach the systemic circulation and can lodge in almost any other part of the body (15%), including the brain.1,2 However, an intracranial hydatid cyst is only found in 1 to 2% of cases. 3 Clinical features are not specific. Depending on the size and location of cysts in the brain, the most common presenting symptoms are headache and vomiting, which are signs of elevated intracranial pressure. Focal neurologic deficits and seizures are less frequent. CT and magnetic resonance imaging are extremely useful to guide the surgical and medical management of hydatid cysts.1,2 Both modalities characteristically show a hydatid cyst as a spherical homogenous, well-defined, nonenhancing cystic lesion without peripheral edema.1,2 When there is edema, it is secondary to a traumatic fissure of the cyst membrane or to a cystic infection. 3 Neither of these conditions was found in our patient. The presence of peripheral edema in our patient may have been related to the extremely large size of this cyst, resulting in increased local pressure, with mass effect causing vascular compression. 4 A second possible explanation is that involution of the cyst caused inflammation of the surrounding nervous tissue with intense gliosis and the presence of macrophages. Inflammation could have created a barrier to nutrient exchange between the host and the parasite, causing peripheral edema. 4 Serology can also be useful to confirm the presence of a hydatid cyst preoperatively. 1 Because hydatid cysts evoke minimal response in brain tissue, many results are falsely negative. 3
Surgery is the mainstay for treatment of intracranial hydatid cysts. Total resection of the cyst via craniotomy, with no membrane rupture, is recommended to prevent recurrence and avoid provoking an anaphylactic reaction. 5 In the Dowling-Orlando technique, the preferred method, lowering the head of the operating table and instilling warm saline between the cyst and the surrounding brain parenchyma deliver the cyst. This is usually possible because there are minimal adhesions around the cyst wall. 6 Postoperative chemotherapy is of utmost importance in preventing recurrences or appearances of new primary cysts. 5 Our patient underwent medical management with albendazole for 6 wk and surgical treatment with excellent results.