Varied types of intracranial hydatid cysts: radiological features and management techniques

Even when radiological images are considered pathognomic for intracranial hydatid cysts, subtle image characteristics are evident depending upon the status/types of hydatid cysts. These imaging features, if finely scrutinized, may help to modify conventional surgical techniques of cyst excision.

From January 2006 to December 2011, nine patients (male:female 7:2, age range 4-44 years, median 7 years) harbouring intracranial hydatid cysts were managed at our centre. In addition to CT scans, all patients underwent plain and contrast-enhanced MRI scans. Based on these radiological findings, the types of hydatid cysts were characterized into simple or complicated (infected) cysts. Complicated cysts were further differentiated into ruptured or intact subtypes based on imaging features. Surgical procedures including the Dowling water dissection technique, in addition to head rotation, were performed for removing these cysts intact.

Children (n = 4) aged 6 years or less presented with increasing head size as the only complaint, while the rest of the patients (n = 5) had symptoms of raised intracranial pressure. MRI features of hypo-intensity on T1-weighted images, hyper-intensity on T2-weighted images, and non-contrast-enhancing cysts were noted for all simple cysts (n = 7), while iso- to mixed intensity on T1-weighted images and hyper-intensity on T2-weighted images with contrast-enhancing pericyst correctly diagnosed all complicated (infected) hydatid cysts (n = 2). One of these complicated cysts had spilled the infected contents outside the cyst wall, but within the confines of the cerebral parenchyma (pericyst). Such a case of contained spontaneously ruptured complicated hydatid cyst is described for the first time. At a median follow-up of 18 months, all patients remain free from cyst recurrence.

Subtle changes in radiological features of CNS hydatid cysts should be appreciated so as to diagnose the type of cyst correctly. The surgical strategy should be tailored according to the type of cyst for favourable outcome.