Intraparenchymal ventricular diverticula in chronic obstructive hydrocephalus: prevalence, imaging features and evolution.

Background: Intraparenchymal cavities communicating with the ventricles may appear in patients with chronic obstructive hydrocephalus despite no identifiable surgerical, vascular or traumatic causes. The rate, features, pathogenesis, evolution and clinical impact of intraparenchymal diverticula have not been outlined, yet.

Methods: Brain MRIs of 130 patients (mean age: 11.3 years; age range: 0-67; 60 females) with chronic obstructive hydrocephalus were analyzed. The pathogenesis, neurosurgical treatment, ventricle size, signs of transependymal reabsorption and septum pellucidum integrity of the hydrocephalus were recorded. Subarachnoid outpouching of the ventricles, post-hemorrhagic parenchymal cavities, paths of ventricular shunting and cavities not communicating with the ventricles were excluded. Of patients with intraparenchymal diverticula, all previous available CT and MRI scans were evaluated.

Results: Eight patients (6.2 %, mean age: 18.7 years; age range: 2-42) harbored 11 intraparenchymal diverticula sprouting from the temporal (6), occipital (3) or frontal (2) horns of the lateral ventricles. Intraparenchymal diverticula were more frequent in males (p = 0.04) and older patients (18.7 ± 12.7 vs 11.3 ± 9.8 years, p = 0.04). Their presence or evolution (mean neuroradiological follow-up 3.6 years; range: 0-8) showed a trend of association with hydrocephalus severity (bifrontal index) and did not correlate with the surgical treatment. In three patients the diverticula progressed during follow-up. One patient presented with hemiparesis consistent with the intraparenchymal lesion and improved after ventricular shunting. A DTI study revealed that the cortico-spinal tract was partly included in the septum between the ventricle and the intraparenchymal diverticulum.

Conclusions: Clinicians dealing with chronic severe obstructive hydrocephalus should be aware of ventricular intraparenchymal diverticulation. Studies aiming at clarifying their pathogenesis and proper management are warranted.