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E1317. Water Cuts Through Rock Not Due to Strength, But Persistence: Two Cases of CSF Auto-Drainage in the Setting of Obstructive Hydrocephalus
Authors
  1. Karun Wadhwa; Mount Sinai Medical Center
  2. Vinay Bhatia; Mount Sinai Medical Center
  3. Paul Couto; Mount Sinai Medical Center
  4. Kunal Patel; Mount Sinai Medical Center
Background
Cerebrospinal fluid (CSF) spaces include ventricles, cerebral and spinal subarachnoid spaces. Hydrocephalus is defined as the accumulation of an abnormal quantity of CSF in the ventricles. There are several disorders that can cause obstructive or nonobstructive hydrocephalus and thus can change the CSF dynamics. CSF auto drainage in the setting of obstructive hydrocephalus is a rare condition. This can compensate for the hydrocephalus by spontaneous communication of a ventricle into a subarachnoid space or through spontaneous CSF rhinorrhea via a meningo-encephalocele (ME). These can be identified by MRI imaging techniques such as phase contrast CSF flow and high resolution isotropic 3D Fast (Turbo) spin T2 weighted sequences (referred to as T2 SPACE hereafter).

Educational Goals / Teaching Points
Understanding CSF production and normal CSF flow pathway. MRI Imaging of hydrocephalus with emphasis on phase contrast CSF flow and T2 SPACE sequences. Differentiating between obstructive and nonobstructive hydrocephalus. Understanding potential CSF auto drainage pathways in the setting of obstructive hydrocephalus.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Case 1: 23-year-old patient with hydrocephalus. Noncontrast CT showed dilated lateral and third ventricles with diffuse effacement of the cortical sulci. T2 SPACE MRI showed heterogenous aqueductal mass with extension into the fourth ventricle and a defect in the posterior wall of the frontal sinus with heterogeneous intracranial signal intensity extending into the left frontal sinus. The patient also had clear left nasal discharge. Findings were consistent with a meningo-encephalocele (ME) causing spontaneous CSF rhinorrhea. Case 2: 36-year-old patient with hydrocephalus. Phase contrast CSF flow MRI showed no CSF flow in the region of aqueduct but showed CSF flow in the floor of the third ventricle. T2 SPACE MRI showed CSF flow between the third ventricle and the interpeduncular cistern and a heterogeneous signal intensity mass in the region of the aqueduct. Patient was asymptomatic, and there was preservation of subarachnoid spaces along the convexities. Overall, findings are most compatible with CSF auto drainage in the setting of long-standing obstructive hydrocephalus between the third ventricle and the interpeduncular cistern.

Conclusion
Long standing obstructive hydrocephalus can decompress by creating new auto drainage pathways as illustrated in these cases. MRI imaging techniques such as phase contrast CSF flow and T2 SPACE sequences can help understand the CSF flow dynamics and identify potential CSF auto drainage pathways in the setting of long standing obstructive hydrocephalus. Obstructive hydrocephalus at the level of cerebral aqueduct can be caused by true aqueductal tumors, pineal cysts, pineal or tectal solid tumors, posterior third ventricular tumors as well as nonneoplastic pathologies such as infections, vascular lesions, and blood clots.