Causes and Diagnosis of Communicating Hydrocephalus

Etiologies and Pathophysiology

• Communicating hydrocephalus is primarily caused by impaired cerebrospinal fluid (CSF) absorption due to fibrosis of arachnoid granulations, meningeal fibrosis, and subependymal gliosis, which can result from various underlying conditions 1
• Post-infectious hydrocephalus is a significant cause, particularly in lower-middle-income countries where it accounts for approximately 19.2% of pediatric hydrocephalus cases 2
• Meningitis leads to inflammation and subsequent fibrosis of the subarachnoid space, impairing CSF flow and absorption 3, 4
• Coccidioidal meningitis can cause hydrocephalus in approximately 40% of affected individuals, either at presentation or during the course of disease 3
• Subarachnoid hemorrhage (SAH) is a major cause of communicating hydrocephalus due to blood products obstructing CSF flow in the subarachnoid space 5, 6
• Intraventricular hemorrhage (IVH), particularly in premature infants, leads to post-hemorrhagic hydrocephalus through impaired CSF absorption 1
• TGF-β1 and TGF-β2 in the CSF stimulate deposition of extracellular matrix proteins, impairing CSF resorption 1
• Elevated levels of aminoterminal propeptide of Type I collagen (PC1NP) have been found in post-hemorrhagic hydrocephalus, consistent with arachnoid granulation fibrosis 1
• Vascular endothelial growth factor levels are elevated in CSF from infants with post-hemorrhagic hydrocephalus 1
• Leptomeningeal metastases can cause communicating hydrocephalus by obstructing CSF flow in the subarachnoid space 7
• Brain tumors, particularly those near the fourth ventricle, can cause communicating hydrocephalus when they partially obstruct CSF flow 8, 2
• Normal pressure hydrocephalus (NPH) is a form of communicating hydrocephalus characterized by the clinical triad of gait disturbance, urinary incontinence, and cognitive impairment 9
• NPH has an estimated prevalence of 3.7% in patients over 65 years of age 9
• Imaging findings include ventriculomegaly, narrowed posterior callosal angle, effaced sulci along high convexities, and widened sylvian fissures 9
• Congenital hydrocephalus can be communicating in nature, with approximately 20% having unclear etiology 10
• Spinal dysraphism is associated with hydrocephalus in approximately 7.6% of pediatric cases across Asia 2

Geographic and Economic Factors

• The proportion of post-infectious hydrocephalus is negatively associated with Human Development Index 2
• The proportion of post-infectious hydrocephalus is negatively associated with urbanization of the country 2
• The proportion of post-infectious hydrocephalus is negatively associated with increasing distance from the equator 2
• Post-infectious hydrocephalus is most common in South Asia (23.2%) 2
• Non-post-infectious causes predominate in East Asia (38.3%) 2
• Dysraphism-related hydrocephalus is most common in West Asia (11.9%) 2

Diagnostic Considerations

• Contrast-enhanced MRI is recommended to evaluate for hydrocephalus and distinguish between communicating and non-communicating types 3, 4
• Ventriculomegaly (not from cerebral atrophy) and transependymal edema are hallmarks of acute hydrocephalus 3
• Lumbar puncture with measurement of opening pressure can help diagnose communicating hydrocephalus 3, 4
• Changes in mental status, nausea, vomiting, cranial neuropathy, incontinence, or gait disturbance should prompt neuroimaging 3

Clinical Implications

• Early diagnosis and surgical treatment are essential for reducing morbidity and mortality 2