What are the causes of communicating hydrocephalus?

Causes of Communicating Hydrocephalus

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

Major Etiologies

Infectious Causes

• Post-infectious hydrocephalus is a significant cause, particularly in lower-middle-income countries where it accounts for approximately 19.2% of pediatric hydrocephalus cases 1
• Meningitis leads to inflammation and subsequent fibrosis of the subarachnoid space, impairing CSF flow and absorption 1
• Coccidioidal meningitis can cause hydrocephalus in approximately 40% of affected individuals, either at presentation or during the course of disease 1

Hemorrhagic Causes

• Subarachnoid hemorrhage (SAH) is a major cause of communicating hydrocephalus due to blood products obstructing CSF flow in the subarachnoid space 1
• Intraventricular hemorrhage (IVH), particularly in premature infants, leads to post-hemorrhagic hydrocephalus through impaired CSF absorption 1, 2
• Blood breakdown products in the CSF stimulate fibrosis of arachnoid granulations, disrupting normal CSF absorption 2

Molecular and Pathophysiological Mechanisms

• 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

Neoplastic Causes

• Leptomeningeal metastases can cause communicating hydrocephalus by obstructing CSF flow in the subarachnoid space 1
• Brain tumors, particularly those near the fourth ventricle, can cause communicating hydrocephalus when they partially obstruct CSF flow 1

Normal Pressure Hydrocephalus

• Normal pressure hydrocephalus (NPH) is a form of communicating hydrocephalus characterized by the clinical triad of gait disturbance, urinary incontinence, and cognitive impairment 1
• NPH has an estimated prevalence of 3.7% in patients over 65 years of age 1
• Imaging findings include ventriculomegaly, narrowed posterior callosal angle, effaced sulci along high convexities, and widened sylvian fissures 1

Congenital and Developmental Causes

• Congenital hydrocephalus can be communicating in nature, with approximately 20% having unclear etiology 3
• Genetic mutations affecting CSF dynamics can lead to communicating hydrocephalus 4
• Spinal dysraphism is associated with hydrocephalus in approximately 7.6% of pediatric cases across Asia 1

Geographic and Economic Factors

• The proportion of post-infectious hydrocephalus is negatively associated with:
  • Human Development Index 1
  • Urbanization of the country 1
  • Increasing distance from the equator 1
• Cultural regions show different patterns of hydrocephalus etiology:
  • Post-infectious hydrocephalus is most common in South Asia (23.2%) 1
  • Non-post-infectious causes predominate in East Asia (38.3%) 1
  • Dysraphism-related hydrocephalus is most common in West Asia (11.9%) 1

Diagnostic Considerations

• Contrast-enhanced MRI is recommended to evaluate for hydrocephalus and distinguish between communicating and non-communicating types 1
• Ventriculomegaly (not from cerebral atrophy) and transependymal edema are hallmarks of acute hydrocephalus 1
• Lumbar puncture with measurement of opening pressure can help diagnose communicating hydrocephalus 1
• Changes in mental status, nausea, vomiting, cranial neuropathy, incontinence, or gait disturbance should prompt neuroimaging 1

Clinical Implications

• Understanding the etiology of communicating hydrocephalus is crucial for appropriate management decisions 5
• Treatment approaches differ based on the underlying cause, with surgical options including CSF shunting and, in some cases, endoscopic third ventriculostomy 5, 6
• Early diagnosis and surgical treatment are essential for reducing morbidity and mortality 1