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Clinical History

A 16-year-old female presented with two months history of progressive headache and difficulty in speaking, to the current state of inability to speak. There was no other significant neurological history. Physical examination revealed Broca’s aphasia with normal motor, sensory, cranial nerve, and cerebellar functions. Contrast-enhanced MRI was subsequently performed.

Imaging Findings

Contrast-enhanced MRI Brain was performed to rule out a space-occupying lesion. It revealed a large, well-defined, Intra axial cystic lesion in the right frontal lobe with multiple floating membranes and multivesicular cysts within. These cysts appear hyperintense on T2 with T2 hypointense walls, representing daughter cysts. There was no diffusion restriction. No contrast enhancement/perilesional oedema/significant mass effect was noted. The above imaging features raised the possible diagnosis of Hydatid cyst. (Fig. 1a and 1b)

Single voxel MR spectroscopy was performed which revealed a pyruvate/succinate peak at 2.4 ppm, thereby confirming the diagnosis. (Fig 2)

MR spectroscopy parameters were as follows - TR = 1000 ms, TE = 144 ms, NEX = 1.00, voxel size = 2.2 cm

Chest X-ray and Ultrasound abdomen were used for screening for hydatid cysts at the aforementioned locations, revealing none.

Post-operative CT revealed no evidence of residual lesion. (Fig 3)

Discussion

Hydatid disease, parasitic infection is a zoonotic disease caused by tapeworms of the genus Echinococcus. The disease is known to be potentially fatal with humans as the accidental intermediate hosts, affecting the liver in most cases and other organs such as the spleen, kidney, lungs, bones, and brain[1].

Intracranial hydatid cyst is rare, accounting for about 1-2% of its clinical manifestations[2,3,4]. Clinical presentation varies widely depending on the site of invasion. They frequently occur in the supratentorial regions, mainly in the middle cerebral artery territory with the parietal lobe being the most common site. Patients present with a wide range of non-specific neurological symptoms such as headache, vomiting, seizures, hemiparesis, visual impairment, altered mental status and features of raised intracranial pressure making a diagnosis difficult [4,5].

Radiological Imaging with CT and MRI demonstrates well-defined, spherical, homogenous cystic lesions with a fluid density similar to the CSF and daughter cysts, a pathognomonic feature of hydatid disease [4]. The cyst wall appears iso dense to hyperdense in contrast to the brain tissue on a CT and produces low signal intensities in T1 and T2 weighted images on an MRI [6]. Contrast enhancement and perilesional oedema are usually absent unless there are secondary complications such as rupture or infection[3]. MRI with MR spectroscopy has now been a leading radio diagnostic tool of choice to distinguish between hydatid cysts and other intracranial pathologies such as cystic neoplasms and abscesses.

MR spectroscopy of the central cystic part of the lesion has shown to have elevated choline, pyruvate, and succinate levels and the peripheral solid part of the lesion increased choline/NAA ratio and a large peak of lipids. Markedly elevated pyruvate peak at 2.48 ppm, the most specific in vivo marker of hydatid infection, and succinate peak at 2.5 ppm are significant features [4,6].

Management of intracranial hydatid cyst involves primarily surgical procedures and long-term use of albendazole to reduce the rate of reoccurrence [7].

Our patient underwent right frontal craniotomy and cyst excision using the Dowling technique. Post-operative CT revealed no evidence of residual lesion.

Histopathological examination revealed the following features of Hydatid cyst - Cyst walls composed of outer lamellated eosinophilic layer and focal inner germinal layer, brood capsules, daughter cysts and scolices bearing hooklets. (Fig. 4)

Complete resolution of aphasia was noted at the time of discharge. The patient was treated with Albendazole and Praziquantel for 4 weeks.

MRI and MR spectroscopy thus serves as a tool not only to differentiate between other pathologies but also to help in defining the anatomical relationship with other structures and multiplicity of cysts to plan definitive surgical intervention.

Written informed patient consent for publication has been obtained.