Hydrocephalus - Axial CT or MR
Hydrocephalus - Axial CT or MR
Search Pattern Assist ?Exam
Purpose
2. Given there is hydrocephalus it needs to be stratified into an internal or external blockade, if possible.
3. Recognize that the volume within 3-dimensional structures (like ventricles) can increase by 7-10% without being detectable. Therefore, we rely on conformational changes in the anterior temporal horn and the lower (hypothalamic) portion of the 3rd ventricle to detect early changes of hydrocephalus.
4. Search for features of elevated CSF pressure: increased edema in the subependymal spaces, optic hydrops, papilledema, and early brain herniation effects.
5. Estimate the grade of ventricular enlargement in obstructive hydrocephalus. Remember, ex vacuo can exist at any level and lacks evidence of elevated CSF pressure. In obstructive hydrocephalus grades between 1-2 are further subdivided in order to assess acutely changing ventricular size prior to surgical intervention (i.e. 1.2/4, 1.4/4, 1.6/4, 1.8/4). Each subdivision adds more subependymal edema, more features of elevated CSF pressure, and more compression of the sulci). At grade-2 (in adults), downward incisural herniation becomes a very real possibility. In children (prior to sutural synostosis) obstructive hydrocephalus can exceed beyond grade-2, by expanding the cranial volume.
6. Search for specific sites of intravenricular block: 1. foramen of Monroe: exclude colloid cyst, subependymal giant cell astrocytoma, glioma involving the rostral septum pellucidum; 2. at cerebral aqueduct: exclude pencil glioma (periaqueductal astrocytoma), congenital aqueductal stenosis, or pineal region masses; in 4th ventricle: caudal 4th vent (medulloblastoma), outlet of the 4th vent: ependymoma, within the 4th vent: racemose neurocystercercosis.
7. Search for evidence of subarachnoid hemorrhage, acute ventriculitis/meningitis, neurosarcoidosis, and meningeal carcinomatosis, all of which are frequently a cause of some degree of hydrocephalus.
8. Search for infectious complicating processes (neurocytercercosis with intraventricular cysts, or infected sequestra); either can cause either ependymal cicatrix with sequestered ventricle, or hydrocephalus at any ventricular level.
9. Detect any intracranial AV shunting lesion; they generally cause some degree of ventricular enlargement based on elevated cerebral venous pressure.
10. Consider NPH (normal pressure hydrocephalus) when persistent but unchanging hydrocephalus (usually has at least some changes of elevated CSF pressure).
11. Resorptive blockade at the level of the arachnoid and pacchionian granulations is usually ascribed to the explanation of external hydrocephalus in the absence of observable reasons for the hydrocephalus.
12. Over-production of CSF can be associated with benign or malignant choroid plexus tumors, as presented in the Introduction to Hydrocephalus lecture
Prior Study
Findings
Axial Non Contrast CT or MR
There is evidence of increased size of all vents (lateral, 3rd, 4th) for age indicating external hydrocephalus. [Yes/No]
There is evidence of specific ventricular obstruction at the level of the 3rd ventricle and/or the foramen of Monroe (including hyperintense colloid cyst on T1-w). [Yes/No]
There is evidence of specific ventricular obstruction at the level of the cerebral aqueduct. [Yes/No]
There is evidence of specific ventricular obstruction at the level of the 4th ventricle. [Yes/No]
There is evidence of early (hyperacute) obstructive hydrocephalus affecting only the anterior temporal horn configuration and expansion of the hypothalamic-segment, 3rd vent. [Yes/No]
There is evidence of grade 1.0/4 to grade 1.6/4 acute obstructive hydrocephalus. [Yes/No]
There is evidence of grade 1.8/4 acute obstructive hydrocephalus likely with impending incisural herniation. [Yes/No]
There is evidence of grade 2/4 acute obstructive hydrocephalus with downward central incisural herniation (displacement of supratentorial structures into the tentorial hiatus). [Yes/No]
There are primary imaging features of elevated intraventricular CSF pressure (subependymal edema, tightened appearance of the ependymal surface, upward bowing the lamina terminalis, downward bowing the tuber cinereum/mammillary bodies (corresponding to the rostral and caudal walls of an expanded lower (hypothalamic portion) of the 3rd vent) distention of the optic and infundibular recesses, and abnormal rotation of the ventrally displaced optic chiasm/visual pathway. [Yes/No]
There may be additional (secondary) imaging features of elevated CSF pressure including optic hydrops, hyperdynamic CSF pulsations, cerebellar tonsillar sagging, and ventricular diverticula. [Yes/No]
Given there is obstructive 4th ventricular enlargement (sequestered vent or obstructing mass), there is now upward incisural herniation. [Yes/No]
There is evidence of epencymal cicatrix with sequestered ventricle under pressure. [Yes/No]
There is evidence of grade 1-4 ex vacuo ventriculomegaly without progressive hydrocephalus. [Yes/No]
There is evidence of subarachnoid or intraventricular acute or subacute blood products with some degree of hydrocephalus. [Yes/No]
There is evidence of arrested or normal pressure hydrocephalus: has stable ventriculomegaly with at least some features of elevated CSF pressure. [Yes/No]
There is unexplained downward incisusal and tonsillar herniation, with or without ventriculomegaly, which is most consistent with intracranial hypotension (ICH). [Yes/No]
NO other significant imaging findings are present. [Yes/No]
