What is Hydrocephalus?
Hydrocephalus is an excessive accumulation of cerebrospinal fluid (CSF) within the brain's ventricles, causing increased intracranial pressure and potential brain tissue damage. 1 This occurs when there is an imbalance between CSF production and absorption, or obstruction to CSF flow 2, 3.
Pathophysiology
The condition results from:
- Impaired CSF circulation or absorption (most common mechanism)
- Obstruction of CSF pathways
- Less commonly, altered CSF production
- Dysfunction in cerebral pulsations and brain compliance 2
Hydrocephalus can be classified as:
- Congenital: Present at or near birth, often linked to aqueduct stenosis or genetic mutations affecting brain development 2, 3
- Acquired: Develops after birth from CNS infection, hemorrhage, tumors, or other pathological processes 2, 3
Clinical Symptoms
In Infants
Progressive macrocephaly (enlarging head circumference) is the hallmark presentation 2, 3. Additional signs include:
- Fontanel fullness and bulging
- Splaying of cranial sutures (particularly sagittal suture)
- Irritability
- Lethargy and decreased activity
- Apnea and bradycardia
- Poor feeding
- Abnormal eye movements (setting-sun sign)
- Hypotonia 4
In Children Over 2 Years
Signs and symptoms of elevated intracranial pressure dominate 2:
- Headache (often worse in morning)
- Nausea and vomiting
- Altered mental status or lethargy
- Gait disturbances (ataxia, difficulty walking)
- Vision disturbances
- Cognitive and developmental delays
- Sleep disturbances
- Urinary incontinence 5, 6
Important Clinical Nuances
The symptom presentation varies by age and etiology. In the context of specific conditions:
Post-hemorrhagic hydrocephalus in preterm infants: May present catastrophically (rapid deterioration), in a saltatory pattern (stuttering progression over days), or be clinically silent requiring surveillance imaging 4
CNS infections (like coccidioidal meningitis): Symptoms of hydrocephalus overlap significantly with meningitis symptoms, creating diagnostic confusion. Approximately 40% of patients with CNS coccidioidal infection develop hydrocephalus 5
Diagnostic Approach
Neuroimaging is essential for diagnosis:
- Infants: Cranial ultrasonography (bedside, safe, avoids transport risks) 4
- Older children: MRI with contrast (preferred) or CT scanning 5
Key imaging findings include:
- Ventriculomegaly (ventricular dilation >12 mm)
- Transependymal edema
- Distinction between communicating vs. non-communicating hydrocephalus 5
Lumbar puncture may reveal elevated opening pressure (>250 mm H2O is concerning), though normal pressure does not exclude hydrocephalus 5
Critical Pitfalls to Avoid
- Do not rely solely on ventricular pressure measurements to exclude hydrocephalus—clinical symptoms combined with imaging are paramount 5
- In infants, clinical signs like fontanel fullness have limited reliability across different practitioners but can be reliable when assessed serially by experienced clinicians 4
- Distinguish hydrocephalus from hydrocephalus ex vacuo (ventricular enlargement from brain atrophy rather than increased pressure) 4
- Unexplained hematocrit decline in preterm infants may be the only clue to intraventricular hemorrhage leading to hydrocephalus 4
Prognosis
Uncontrolled hydrocephalus leads to macrocephaly, developmental delays, and neurological deficiencies affecting quality of life and survival 1. Long-term outcomes depend heavily on:
- Underlying etiology
- Timeliness of diagnosis and treatment
- Presence of associated anomalies 7
Early surgical intervention (CSF shunting or endoscopic third ventriculostomy) remains the mainstay of treatment and is critical for reducing morbidity and mortality 1, 3.