In children with congenital malformations that do not allow CSF to flow properly, or In adults or children, when …
Tumors or blood clots obstruct CSF circulation, or
As a result of injury or infection
Obstructive hydrocephalus typically is caused by a blockage in the normal circulation of CSF within the brain. This can be due to scarring of a ventricle or a tumor. When the obstruction is due to a tumor, it is important to realize that the tumor has only a 10% chance for growth and the only treatment required is for the hydrocephalus.
Examples: Pineal germinoma
Obstructive hydrocephalus secondary to enlarged Virchow Robin space (VRS) is a rare entity, with only a handful of cases reported in the literature. Presenting symptoms varies widely from headaches, through to dizziness.
Donaldson et al. report a 31 year old male who presents with pulsatile tinnitus and an MRI showing obstructive hydrocephalus secondary to tumefactive VRS. After a CSF diversion procedure in the form of an ETV he had almost complete resolution of his symptoms.
This is the first case of obstructive hydrocephalus secondary to enlarged Virchow-Robin spaces, presenting with pulsatile tinnitus 1).
Twenty-one patients with obstructive hydrocephalus were evaluated with MR diffusion imaging before and after treatment. The change in ventricular size was measured by using the frontal and occipital horn ratio. The signal intensity abnormalities in periventricular white matter were scored. Average diffusion constants (D(av)) in the periventricular white matter were measured before and after treatment and compared with normal values. Post-treatment resolution of MR imaging abnormalities and changes in ventricular volume were compared with changes in D(av).
D(av) measured from periventricular white matter was increased in hydrocephalic patients compared with age-matched control subjects by a mean of 6.9% (P <.02). After treatment, D(av) decreased by an average of 6.0%: D(av) decreased in 11 patients (53%), it remained essentially unchanged in seven (33%), and it increased in three (14%).
For patients with obstructive hydrocephalus, diffusion is usually increased in the periventricular white matter. Therefore, increased D(av) may be a clinically useful sign of hydrocephalus, and it may prove useful in cases with equivocal clinical or imaging findings. Measurement of D(av) may be valuable in assessing the treatment response in these patients because D(av) usually decreases toward normal levels with successful treatment 2).