Background

The brain and spinal cord, which are essential parts of the central nervous system, are remarkably malleable and have the capacity to regenerate after damage. The brain and spinal cord must interact for there to be motor control and coordination.

Recent studies provide insight into a number of structural, functional, disease- and damage-related issues. Severe and long-lasting effects, such as cognitive, emotional, and physical disabilities, can result from brain and spinal cord damage.

This article delves into the complex link between meningitis and hydrocephalus. Providing light on their causes, symptoms, diagnostic techniques and treatment choices, with a special emphasis on how meningitis can lead to the development of hydrocephalus.

Introduction

Meningitis is a medical condition in which the protective membranes that cover the brain and spinal cord are inflamed. The infection in meningitis results because of an array of infectious agents, which includes bacteria, viruses, and fungi, among others, or noninfectious agents such as certain drugs and diseases.¹ 

The meninges are made up of three membranes - the dura mater, arachnoid mater, and pia mater. The meninges protect the central nervous system and contain cerebrospinal fluid, which acts as a cushion for the brain and spinal cord.

The country, region, age group and pathogen all affect the infection rate. The frequency of meningitis, in children under five varies between 0.07 to 2.5%. In underdeveloped nations, there is a high rate of morbidity and mortality.²

A medical disorder called hydrocephalus is defined by an abnormal build-up of cerebrospinal fluid (CSF) inside the brain's ventricles. Important fluid-filled compartments in the brain, the ventricles are involved in brain development, function, and disease. Cerebrospinal fluid, or CSF, is produced and circulated by them, and it is necessary to preserve homeostasis and safeguard the brain. This build-up of fluid causes increased pressure inside the skull, which can lead to the brain swelling and potential damage to brain tissues.³ Hydrocephalus can be present at birth or acquired later in life. 

Hydrocephalus occurs when there is an excessive accumulation of cerebrospinal fluid (CSF) within the brain's ventricles. The ventricles are cavities or spaces inside the brain. Normally, CSF circulates around the brain and spinal cord, providing essential functions such as cushioning the brain, removing waste products, and delivering nutrients. Under normal bodily conditions, the rate of production and absorption are always balanced.

Hydrocephalus occurs when the balance is disrupted, leading to a buildup of CSF. This can occur due to several reasons, such as:

• CSF cannot circulate correctly due to an obstruction in its flow, which frequently occurs within the small spaces that link the ventricles. We refer to this condition as non-communicating or obstructive hydrocephalus
• The body is unable to properly absorb CSF into the bloodstream, leading to an excess of fluid. This type is called communicating hydrocephalus
• In rare cases, the brain produces too much CSF, overwhelming the absorption rate

The accumulation of fluid increases the pressure within the brain, which can compress and damage brain tissue. If this condition is left untreated, it can result in various symptoms, including cognitive decline, difficulty walking, and, in severe cases, permanent brain damage or death.³ 

Global prevalence of meningitis and hydrocephalus

The epidemiology of meningitis and hydrocephalus reveals significant disparities in incidence rates globally, particularly affecting low- and middle-income countries (LMICs) in Sub-Saharan Africa and Asia. These regions experience higher burdens due to various factors, including limited healthcare resources and endemic pathogens.

• The incidence of meningitis is high in Sub-Saharan Africa due to epidemics caused by group-A meningococci, with attack rates up to 500/100,000. Hydrocephalus can be a sequelae of meningitis⁴
• In Sub-Saharan Africa, approximately 700,000 cases of meningitis have been reported, with N. meningitidis responsible for a significant portion⁵
• Cryptococcal meningitis is prevalent among HIV-infected populations in Uganda, accounting for 60% of meningitis cases, highlighting the intersection of infectious diseases and socio-economic factors ⁶
• The introduction of vaccines in these regions has been hampered by competing health priorities and funding limitations, exacerbating the disease burden⁵

Understanding meningitis

There are different types of meningitis, each causing different symptoms with different levels of severity. The classification is based on the specific causative agent. 

Viral meningitis

• The primary cause is by enteroviruses eg, echovirus, Coxsackievirus, poliovirus, etc. But also includes herpes viruses, influenza, and arboviruses
• Symptoms: often resemble flu-like conditions, including headache, fever, neck stiffness, and fatigue. Severity varies, particularly in infants ¹

Bacterial meningitis

• The most common pathogens are Streptococcus pneumoniae and Neisseria meningitidis ⁷, with Escherichia coli prevalent in neonates
• This type is more severe than viral meningitis, with rapid onset and high mortality rates if untreated

Fungal and parasitic meningitis

• Fungal meningitis is rare and typically affects immunocompromised individuals, while parasitic meningitis, though infrequent, can be life-threatening. Examples include Cryptococcus neoformans, Candida albicans, Histoplasma capsulatum, Coccidioides immitis, etc
• Both types are less common and often linked to specific risk factors, such as compromised immune systems or environmental exposure¹

While viral meningitis is generally less severe, bacterial meningitis poses significant health risks, necessitating prompt medical intervention. Fungal and parasitic forms, although rare, highlight the diverse etiologies of meningitis.

Common symptoms

• Fever is present in most pediatric cases
• Headache and stiff neck are classic signs, indicating meningeal irritation
• Some additional symptoms include nausea, vomiting, photophobia, and altered mental status may also occur

Importance of early detection

• Bacterial meningitis can deteriorate within hours, necessitating immediate medical intervention¹
• Lumbar puncture is essential for confirming meningitis, although imaging studies like CT scans may be used to assess complications

Recognising these symptoms early can significantly improve outcomes, particularly in bacterial cases, where timely antibiotic treatment is critical. However, it is important to note that not all patients present with classic symptoms, especially in vulnerable populations like infants and the elderly.

Diagnosis of meningitis

Lumbar puncture (spinal tap), and imaging studies.

The diagnosis of meningitis involves a thorough clinical evaluation and the use of various diagnostic tests. 

Clinical evaluation

• Common symptoms include headache, nausea/vomiting, and neck stiffness
• Some signs include neurological deficits and altered mental status, which may suggest increased intracranial pressure, necessitating careful evaluation

Diagnostic tests

• Lumbar Puncture: This is the gold standard for diagnosing meningitis, allowing for cerebrospinal fluid (CSF) analysis. The CSF fluid usually has the following characteristics: low glucose/sugar (less than 2.5 mmol/L), high protein content (more than 500 mg/dl), pleocytosis (white blood cells greater than 1000/microliters), high opening pressure, and a CSF: serum glucose ratio of less than 0.4. The CSF can undergo gram staining and culture in instances of suspected meningococcal meningitis⁴
• CT scans and MRI, particularly contrast-enhanced FLAIR sequences, have shown high sensitivity (91%) and specificity (85%) in diagnosing meningitis.⁸ Additionally, multiplex PCR has demonstrated 94% sensitivity and 100% specificity for differentiating bacterial from viral meningitis¹ 

FAQs

What is the relationship between meningitis and hydrocephalus?

Mechanisms behind the development of hydrocephalus post-meningitis. Meningitis, particularly tuberculous meningitis (TBM), is a significant precursor to hydrocephalus due to the inflammatory processes and complications that arise during the infection. The mechanisms leading to hydrocephalus post-meningitis involve both obstructive and communicating types, primarily driven by inflammatory responses and cerebrospinal fluid (CSF) dynamics.⁹ While hydrocephalus is a common complication of meningitis, it is essential to consider that not all cases lead to this outcome. Some patients may recover without significant neurological deficits, emphasising the variability in individual responses to meningitis.

Are there treatment options available?

Treatment of viral meningitis

• Most cases of viral meningitis are self-limiting, requiring only symptomatic management such as hydration, pain relief, and rest¹
• The overall prognosis for viral meningitis is generally favorable, with most patients recovering fully without specific antiviral treatment

Treatment of bacterial meningitis

• Bacterial meningitis is a medical emergency that demands prompt initiation of empiric antibiotics tailored to the most likely pathogens, such as Streptococcus pneumoniae and Neisseria meningitidis. Third-generation cephalosporins are proven effective against meningitis
• Instances of delayed treatment can significantly increase mortality rates, emphasising the need for rapid diagnosis and intervention.

Hydrocephalus treatment

Hydrocephalus treatment often involves two primary surgical interventions: ventriculoperitoneal shunt (VPS) placement and endoscopic third ventriculostomy (ETV). Each method has distinct indications and procedural characteristics that influence patient outcomes.¹⁰

Ventriculoperitoneal shunt (VPS)

VPS involves implanting a device to divert cerebrospinal fluid (CSF) from the ventricles to the peritoneal cavity. This method is commonly used for various hydrocephalus etiologies, including intraventricular hemorrhage and neural tube defects.¹¹

Endoscopic third ventriculostomy (ETV)

ETV is a minimally invasive procedure that creates an opening in the third ventricle, allowing CSF to bypass obstructions. It is particularly effective for obstructive hydrocephalus and has shown lower infection rates compared to VPS.¹² 

Summary

Meningitis is the inflammation of the membranes surrounding the brain and spinal cord, caused by infectious agents like bacteria, viruses, and fungi, or noninfectious factors such as certain drugs. It affects different age groups and regions, with bacterial meningitis being the most severe, often caused by Streptococcus pneumoniae and Neisseria meningitidis. Viral meningitis, while generally less severe, still presents flu-like symptoms such as fever, headache, and neck stiffness. Fungal and parasitic forms are rare, mainly affecting immunocompromised individuals. Early diagnosis is critical, with lumbar puncture being the key diagnostic tool. While imaging studies help identify complications. 

Hydrocephalus is a condition characterised by excessive cerebrospinal fluid (CSF) in the brain, which often occurs after meningitis due to disrupted CSF flow. Treatment of meningitis depends on the type, with viral cases requiring symptomatic care and bacterial cases demanding prompt antibiotic therapy. For hydrocephalus, surgical interventions like ventriculoperitoneal shunts or endoscopic third ventriculostomy are used to relieve pressure. Early detection and treatment are vital to preventing severe outcomes in both conditions.