Hydrocephalus: Male Predominance, Risk Factors, and Pathophysiology

Hydrocephalus (excessive CSF accumulation in cerebral ventricles) shows a male predominance of approximately 3:2 (1.5:1) across most types and age groups.

Proposed Mechanisms for Male Bias

• Genetic: X-linked genes (e.g., L1CAM causing X-linked hydrocephalus) affect males exclusively. Other susceptibility loci may have sex-biased expression.
• Hormonal: Androgens may influence CSF production (choroid plexus), arachnoid villi maturation, or ventricular development. Estrogen may be neuroprotective.
• Developmental: Male fetal brain grows faster/larger; ventricular system may be more vulnerable to obstructive lesions (aqueductal stenosis).
• Intraventricular hemorrhage (IVH): Preterm males have higher IVH rates → post-hemorrhagic hydrocephalus.

Major Risk Factors (All Ages)

Category	Examples
Congenital	Aqueductal stenosis, Chiari malformation, Dandy-Walker, neural tube defects, intrauterine infection (TORCH), genetic syndromes.
Acquired - Infant/Child	IVH (prematurity), meningitis, brain tumors (posterior fossa), trauma, vascular malformations.
Acquired - Adult	Subarachnoid hemorrhage, traumatic brain injury, tumors, meningitis, Normal Pressure Hydrocephalus (NPH—idiopathic, >60 yrs).

Clinical Implications

• Male infants: Higher index of suspicion for rapid head growth, bulging fontanelle, sunset sign.
• Genetic counseling for X-linked forms (L1CAM—MASA syndrome, spastic paraplegia).
• NPH: Slight male predominance; triad of gait apraxia, urinary incontinence, dementia. Shunt-responsive.

The 3:2 ratio is consistent but not absolute; etiology-specific ratios vary. Early diagnosis and CSF diversion (shunt, ETV) improve neurodevelopmental outcomes.