Hydrocephalus

Cerebrospinal fluid is a clear fluid that cushions the brain and spinal cord, carries nutrients, and removes waste. Under normal circumstances, it circulates through the ventricular system and is then absorbed into the bloodstream. Hydrocephalus develops when this circulation or absorption is disrupted and CSF accumulates instead — raising pressure inside the skull and, in untreated or progressive cases, damaging brain tissue.

The condition is not one disease but the end result of several different processes. Congenital hydrocephalus is present from or shortly after birth, often due to a narrowed cerebral aqueduct, spina bifida, or another developmental abnormality affecting CSF pathways. Acquired hydrocephalus arises later: haemorrhage within or around the brain (including intraventricular haemorrhage related to prematurity), meningitis or other brain infections that scar the absorption surfaces, or a brain tumour, cyst, or head injury that physically obstructs or disrupts flow. In some patients no definite cause is ever identified.

A distinct form, normal-pressure hydrocephalus (NPH), affects older adults. Here the ventricles enlarge but the CSF pressure measured at lumbar puncture is not markedly elevated — the classic triad is walking difficulty, cognitive slowing, and bladder disturbance, developing gradually and often mistaken for Parkinson's disease or Alzheimer's.

The presentation depends heavily on age, because a baby's skull sutures are still open and can expand to accommodate rising pressure, while an adult's fused skull cannot. Recognising the pattern for each age group is essential to timely diagnosis.

In babies, the cardinal signs are a rapidly increasing head circumference, a tense or bulging fontanelle (the soft spot on top of the skull), prominent scalp veins, downward-looking eyes (sometimes called 'sunsetting'), irritability, poor feeding, vomiting, and excessive sleepiness.

In older children, symptoms shift toward morning headache, nausea or vomiting, blurred or double vision, difficulty looking upwards, balance problems, a decline in school performance, and changes in behaviour or personality.

In adults, persistent or worsening headache — often worse in the morning or on lying flat — blurred vision, increasing sleepiness, confusion, memory difficulty, and trouble walking or maintaining balance are the common presenting complaints. The tempo can be acute (hours to days) or chronic (weeks to months), and the distinction has urgent implications for management.

In normal-pressure hydrocephalus, the classic Hakim-Adams triad — gait disturbance (typically a shuffling, magnetic gait), cognitive impairment (slowing, forgetfulness, executive dysfunction), and urinary urgency or incontinence — develops insidiously over months to years. Because these symptoms overlap with common neurodegenerative conditions, the diagnosis is often missed or delayed unless specifically sought.

Diagnosis combines a detailed history, neurological examination, and imaging. CT or MRI shows ventricular enlargement; the pattern of dilatation — whether all ventricles are involved, whether the temporal horns are disproportionately enlarged, and whether there is evidence of transependymal CSF flow (a rim of signal change around the ventricles suggesting acute pressure) — helps distinguish hydrocephalus from atrophy and guide the urgency of intervention.

In babies, serial head circumference measurements plotted on a growth chart are a simple, low-cost surveillance tool. In children, developmental assessment and ophthalmology review for papilloedema are added. In suspected NPH, formal gait assessment, cognitive testing, and a lumbar puncture — sometimes with a period of temporary CSF drainage — help predict who will benefit from a shunt. CSF pressure measurement and drainage response are central to the NPH work-up, since imaging alone does not establish the diagnosis.

The two principal surgical options are endoscopic third ventriculostomy (ETV) and ventriculoperitoneal (VP) shunting. The choice depends on the site of obstruction, the underlying cause, the patient's age and anatomy, and the surgeon's assessment of which approach offers the best balance of benefit and risk for that individual.

In ETV, a small endoscope is passed into the third ventricle and a new opening is created in its floor, allowing CSF to bypass an obstruction and flow through a natural pathway toward the absorptive surfaces. No permanent tubing or valve is implanted. ETV is best suited to obstructions within the ventricular system itself, such as aqueductal stenosis, where the downstream absorptive pathways remain functional.

VP shunting diverts excess CSF from a ventricle to the abdominal cavity through a system of narrow silastic tubing and a pressure-regulated valve. The valve is set to open at a specific pressure, draining only when needed. VP shunts are suitable for most causes of hydrocephalus and remain the more established option when ETV is not appropriate — for example, when the obstruction lies beyond the ventricles or when absorptive failure (rather than a physical blockage) is the dominant problem.

Temporary external ventricular drainage may be needed before a permanent treatment is chosen, particularly after a haemorrhage or infection when the clinical picture is still evolving.

Both operations carry real risks — infection, obstruction, overdrainage, underdrainage, and the need for revision surgery at any point in the patient's life. These are discussed candidly beforehand, because the patient or family must recognise the warning signs of failure for the rest of their lives.

Recovery after ETV or VP shunt surgery typically involves a hospital stay of several days to around a week, with close neurological observation and serial imaging to confirm the ventricles are responding. Children return to school within weeks; adults to desk-based work within two to four weeks.

A central concept that every patient and family must understand: both ETVs and shunts can fail months or years after apparently successful treatment. Previous symptoms often return in the same pattern when a shunt blocks or an ETV closes, and patients and families learn to recognise their own warning signs. The signs that demand immediate emergency assessment include: severe or rapidly worsening headache with repeated vomiting, increasing drowsiness or difficulty waking, new confusion, weakness, or seizure, sudden visual deterioration, a tense or bulging fontanelle or rapid head enlargement in a baby, and clear fluid leaking from a wound or redness and swelling over a shunt with fever.

Follow-up is lifelong. Children are followed through growth, with shunt revisions anticipated as part of the natural history rather than as a failure of the original operation. Adults are monitored with periodic imaging and clinical review. The goal is not simply a functioning shunt or a patent ETV — it is a person living their life with the condition managed, not defined by it.