Cerebral hydatid disease

Cerebral hydatid disease (neurohydatidosis) is caused by Echinococcus granulosus or less commonly E. alveolaris or E. multilocularis. The larval stage is the cause of hydatid disease in humans ¹.

For a general discussion, and for links to other system specific manifestations, please refer to the article on hydatid disease. 

Epidemiology

Cerebral hydatid disease is a rare parasitic infestation and accounts for 1-2 % of all cystic echinococcosis. Hydatid disease is endemic in the Mediterranean region, the Middle East, Africa, eastern part of Turkey, Australia and parts of South America ².

Clinical presentation

Symptoms and signs include:

• focal neurological deficits
• headaches
• increased intracranial pressure
• hydrocephalus
• papilledema and loss of vision
• altered mental status
• seizures (rare)

Pathology

The infection is acquired via contaminated food with eggs of the tapeworm. The oncospheres released from the eggs in the bowel enter the portal circulation. Hence the liver is most commonly affected, followed by the lung. Other organs may be infected as bones, genitourinary system, bowel and even subcutaneous tissues.

Intracranial hydatid disease is very rare. Most cerebral hydatid cysts are located in supratentorial structures in the vascular territory of middle cerebral artery ¹.

Types

Intracranial hydatid cysts can be classified into:

• primary hydatid cysts
  • ​occur as direct invasion of larva that managed and filtered via liver and lung to the brain
  • usually solitary but may be multiple
  • is fertile
• secondary hydatid cysts
  • ​occur as a result of rupture of primary cysts in other organs then reaching by embolization to the brain
  • usually multiple
  • infertile
  • do not have brood capsule or scolices

Radiographic features

MRI

Described features include:

• well-defined circumscribed spherical non-enhancing intra-axial cystic lesion
• lies in the territory of the middle cerebral artery
• cyst fluid is isointense with CSF in all pulse sequences
• no calcification or and typically no surrounding edema
  • presence of perilesional edema usually indicates complication as rupture or secondary infection

Treatment and prognosis

Management is surgical, with removal of the entire cyst without rupture using Dowling’s maneuver (instilling warm saline between the cyst wall and the brain) ⁵. In some cases where it is felt that removing the cyst intact (without cyst rupture during surgery) is unlikely to succeed, the cyst can be removed after puncture and aspiration of its contents. 

Serology and histopathology of the excised cyst will confirm the diagnosis of neurohydatidosis.

Rupture of the cyst can result in recurrence in the subarachnoid space, both intracranially and of the spine (see spinal hydatid disease) ⁶. 

Differential diagnosis

Considerations include:

• pyogenic or fungal abscess
• primary brain tumor: e.g. cystic astrocytoma
• cystic granulomas
• arachnoid cyst
• porencephalic cyst