Types Of Hydrocephalus

Introduction 

Hydrocephalus, refers to “water on the brain”, which means the excessive accumulation of cerebrospinal fluid (CSF) within the brain ventricles, leading to increased intracranial pressure, and various neurological dysfunctions. When not treated properly, it is even life-threatening. Hydrocephalus can be classified into different subtypes based on its onset, causes, and the affected brain areas, which is crucial for accurate diagnosis and effective treatment. Hydrocephalus is classified as congenital, acquired, communicating, non-communicating, normal pressure hydrocephalus, and hydrocephalus ex-vacuo to promote early recognition and medical attention, facilitating a better prognosis among the affected population.¹

Congenital hydrocephalus 

Congenital hydrocephalus is a condition in which CSF is abnormally accumulated within brain ventricles at birth or shortly afterwards. 

Various factors contribute to congenital hydrocephalus such as genetic abnormalities, aqueductal stenosis, neural tube defect, premature birth, chiari malformation, and prenatal infections (e.g., rubella), where normal CSF flow and absorption is obstructed. An enlarged head and bulging fontanel an often sight of a person with hydrocephalus due to fluid pressurization. This causes brain damage which potentially leads to motor delays, cognitive impairments, seizures, sunsetting eyes.¹

Amniocentesis can detect the presence of hydrocephalus-associated defects before birth. Imaging techniques such as ultrasound, CT, or MRI scans can also detect abnormal fluid accumulation postnatally. Treatment for congenital hydrocephalus varies based on its severity, however ,it is generally not treated until after birth as surgical procedures such as ventriculoperitoneal (VP) shunt or endoscopic third ventriculostomy (ETV) are involved to facilitate CSF reabsorption by other body parts.^2,3

Acquired hydrocephalus 

Acquired hydrocephalus develops at any point after birth, across people of all ages. It is commonly caused by head trauma, infections (meningitis or encephalitis), stroke, tumours, arachnoid cysts or masses that block the flow of CSF, resulting in its accumulation and increased intracranial pressure.^1,4

The treatment options depend on the underlying causes, which include headache, nausea, lethargy, gait and visual disturbances, cognitive and personality changes, and balance and coordination issues. Prompt medical attention and diagnosis are vital to prevent further neurological damage.¹

Similar to congenital hydrocephalus, the diagnosis of acquired hydrocephalus involves a comprehensive medical history evaluation, and CT, MRI, and ultrasound imaging scans. Lumbar puncture and intracranial pressure monitoring (ICP) are also performed to facilitate treatment decisions.¹

Surgical removal of a tumour or blockage, VP shunt insertion or ETV procedures are employed to relieve intracranial pressure and restore flow of CSF.⁴

Communicating hydrocephalus 

Communicating (non-obstructive) hydrocephalus occurs when CSF flow is blocked after exiting the ventricles. Normal CSF flow from spinal to cortical subarachnoid spaces is blocked by the thickened arachnoid membrane.^1,5

Common causes of communicating hydrocephalus are post-hemorrhagic, post-inflammatory changes, subarachnoid hemorrhage, bacterial meningitis, or brain surgery complications.⁶ Despite the free flow of CSF in the ventricles, the impaired absorption to the bloodstream can cause accumulation and enlargement among ventricular tissues, resulting in increasing ICP.

Symptoms of communicating hydrocephalus include a headache that worsens in the mornings, nausea, vomiting, gait disturbances, papilledema, and cognitive, and behavioural changes. 

Despite the conventional imaging techniques, lumbar puncture and fundoscopy (to view optic nerve ) will also be employed upon diagnosis. While ETV is not suitable for most of the communicating hydrocephalus, surgical placement of VP shunt is generally used to divert excessive CSF to other body parts (e.g., abdominal cavity) for absorption. 

Non-communicating hydrocephalus 

Non-communicating (obstructive) hydrocephalus occurs when the CSF is blocked along one or more narrow passages in the ventricular regions. This leads to accumulation of CSF causing increased intraventricular pressure.¹

While CSF pathway blockage can occur at different points, usually it happens during aqueductal stenosis.It can also happen when there are tumours, cysts, infections, or bleeding in the brain. 

Imaging techniques, lumbar puncture and fundoscopy are typically used for diagnosis.¹

The specific symptoms of non-communicating hydrocephalus are headache, vomiting, nausea, altered mental status, and visual disturbances along with enlarged head circumference and bulging fontanelles.. 

While blockage removal or bypassing surgeries are generally used to treat non-communicating hydrocephalus, VP shunt placement or ETV procedure can also help to relieve ICP and restore normal flow of CSF.^1,5

Normal-pressure hydrocephalus

Normal-pressure hydrocephalus (NPH) is a subtype of communicating hydrocephalus , when excessive CSF accumulates within the skull slowly over time, leading to enlarged brain ventricles, pressurising the brain and disrupting neurological functions. However, due to the gradual drainage, ICPin NPH is usually not as high as other hydrocephalus forms.^7,8

NPH generally affects older adults, either idiopathic, or secondary to brain aneurysm, stroke, brain tumour, traumatic brain injury (TBI), infections, brain surgery, and even neurodegenerative diseases, such as Alzheimer’s disease or Lewy body dementia.⁷ 

The three main symptoms of NPH are termed as Hakim's triad which are gait issues (similar to Parkinson’s disease), urinary incontinence, and cognitive difficulties (resembling dementia). They (usually start gradually and worsen over months. 

Due to its shared symptoms with dementia and other neurodegenerative conditions, diagnosing NPH is often tricky. A comprehensive approach including physical and neurological exams, thorough medical history and symptomatic evaluation, MRI, CT, cisternogram scans, and lumbar puncture are used to rule out other conditions while diagnosing NPH.

Idiopathic NPH is usually treatable with VP shunt in diverting excessive CSF commonly to the peritoneum or pleural membrane (occasionally)Treatment and its effectiveness towards secondary NPH is highly dependent on the underlying causes. 

Hydrocephalus ex-vacuo

Hydrocephalus ex-vacuo is a condition that leads to a compensatory increase of CSF volume within the skull post- stroke, injuries or neurological conditions, and brain tissue loss.^8,9

Typically caused by conditions such as multiple strokes, Alzheimer’s, multiple sclerosis , leukodystrophy, and other neurodegenerative conditions. When brain tissues are lost, the extra empty spaces are then filled by CSF, resulting in ventricular enlargement. Although there is more CSF than usual, unlike other hydrocephalus subtypes, the ICP may or may not elevate in hydrocephalus.⁸

Signs and manifestations of hydrocephalus ex-vacuo are highly dependent upon its causes and the extent of brain tissue loss. It commonly includes motor deficits, cognitive declines, behavioural, personality or emotional changes, as well as other neurological symptoms associated with the underlying conditions⁸. 

The first and foremost treatment and progression control of hydrocephalus ex-vacuo is still based on underlying condition management. In some cases, rehabilitation therapies or medications are implemented to improve symptoms.

Comparing hydrocephalus subtypes 

The aforementioned hydrocephalus subtypes share some commonalities while differing in various aspects. 

Similarities 

All hydrocephalus subtypes involve the abnormal and excessive accumulation of CSF within the brain ventricles, leading to ventricular enlargements, increased ICP and potential neurological complications. 

Differences 

Causes

Challenges in diagnosis and management 

As symptoms overlap with other conditions, diagnosing hydrocephalus can be challenging. Imaging techniques such as ultrasound, CT, or MRI scans are commonly used. Typical management involves surgical removal, VP shunt placement or endoscopic procedures. However, ongoing monitoring and potential revision surgeries are needed during possible shunt malfunction or infection. Due to its resemblance to other neurological disorders, diagnosing NPH can be challenging, in which differential diagnosis and response to shunt placement are important. Hydrocephalus ex-vacuo is largely addressed through rehabilitation therapies and progression management to the underlying cause for brain tissue loss. 

Prognosis and long-term outcomes 

Prognosis varies depending on hydrocephalus subtypes and individual circumstances. Congenital hydrocephalus may require lifelong management, while acquired hydrocephalus depends totally on the underlying cause. Furthermore, the outcomes of communicating and non-communicating hydrocephalus differ according to the success of surgical interventions. NPH outcomes depend on timely diagnosis and appropriate treatment. Hydrocephalus ex-vacuo outcomes largely depend on the progression of brain tissue loss. 

Impact on quality of life 

Quality of life can be significantly compromised across all subtypes. Individuals may experience cognitive impairments, motor issues, visual disturbances, behavioural and emotional changes, and other neurological deficits. The extent of impacts varies based on hydrocephalus severity and treatment effectiveness. 

Summary 

Hydrocephalus encompasses various subtypes: congenital, acquired, communicating and; non-communicating,normal-pressure hydrocephalus, and hydrocephalus ex-vacuo. Despite their differences, all types involve abnormal CSF accumulation within brain ventricles, resulting in increased ICP. Although prognosis and impact on quality of life vary among subtypes, timely diagnosis, surgical interventions, ongoing monitoring by neurosurgeons, neurologists, rehabilitation specialists, and comprehensive support from caregivers are vital. Continuous research, increased awareness, diagnosis and rehabilitation advancements are also essential in optimising outcomes and quality of life among the hydrocephalus population.