How can a viral pharyngitis lead to meningitis?

How Viral Throat Infections Lead to Meningitis

Viral pharyngitis can progress to meningitis when certain neurotropic viruses—particularly enteroviruses, herpes simplex virus (HSV), varicella-zoster virus (VZV), Epstein-Barr virus (EBV), and mumps virus—spread from the oropharynx to the central nervous system through hematogenous dissemination or, in the case of herpes viruses, via retrograde neuronal transmission from cranial nerve ganglia.

Pathophysiological Mechanisms

Primary Routes of CNS Invasion

The connection between viral pharyngitis and meningitis occurs through two main pathways:

Hematogenous spread is the predominant mechanism for most viruses causing meningitis. After initial replication in the oropharyngeal mucosa, viruses enter the bloodstream (viremia) and subsequently cross the blood-brain barrier to reach the meninges 1, 2. This is particularly characteristic of:

• Enteroviruses (over 90 serotypes), which are transmitted via the fecal-oral route but can replicate in the throat, causing pharyngitis as a prodromal symptom before systemic dissemination 1, 2
• EBV and mumps virus, which commonly present with sore throat as part of their clinical syndrome before meningeal involvement 1

Retrograde neuronal transmission is the mechanism specific to herpes viruses. HSV and VZV can spread from the oropharynx or cervical ganglia in a retrograde fashion through cranial nerves to reach the meninges 3. This explains why:

• VZV meningitis is transmitted primarily via the respiratory route and can occur with or without the characteristic rash 1
• HSV-2 meningitis can occur during primary infection or reactivation, with patients rarely having concurrent genital ulcers 1
• HSV-1, while more commonly associated with encephalitis, can also cause meningitis through similar neuronal pathways 1, 3

Clinical Recognition

Key Distinguishing Features

When viral pharyngitis progresses to meningitis, patients develop the classic triad of meningism:

• Neck stiffness, headache, and photophobia are the hallmark symptoms 1, 4
• Fever may or may not be present—its absence does not exclude viral meningitis 1, 4
• Sore throat, along with diarrhea, vomiting, and muscle pain, often persists as non-specific accompanying symptoms 1

The critical distinguishing feature is preserved consciousness—any alteration in mental status suggests bacterial meningitis, encephalitis, or other intracranial pathology rather than uncomplicated viral meningitis 1, 4.

Common Pitfalls to Avoid

• Do not rely on Kernig's or Brudzinski's signs, as they have extremely low sensitivity (11% and 9% respectively) for diagnosing meningitis 4, 5
• Do not assume the absence of classic symptoms rules out meningitis, as presentations can be atypical, especially in elderly patients 5
• Do not delay lumbar puncture if bacterial meningitis cannot be excluded, as empiric antibiotics should be started immediately while awaiting diagnostic confirmation 4, 5

Diagnostic Approach

When viral pharyngitis is suspected to have progressed to meningitis:

CSF analysis via lumbar puncture is mandatory and should include 4, 5:

• Opening pressure measurement
• Cell count (typically shows pleocytosis with lymphocytic predominance, though early presentations may show neutrophil predominance) 3
• Biochemistry (glucose and protein)
• CSF PCR for enteroviruses, HSV-1, HSV-2, and VZV—this is the gold standard for diagnosis 1, 4

Throat swabs should be tested for enterovirus by PCR to support the diagnosis when CSF testing is performed 1

Important caveat: No causative pathogen is identified in 30-50% of presumed viral meningitis cases despite appropriate testing, which does not exclude the diagnosis if clinical and CSF findings are consistent 1, 5.

Management Implications

Identifying the viral pathogen allows for cessation of unnecessary antibiotics, reduces additional investigations, and shortens hospital stays 1, 4. However, there are currently no treatments of proven benefit for most causes of viral meningitis 4. While some clinicians treat herpes meningitis with aciclovir or valaciclovir, evidence supporting this practice is lacking, and these agents should not be used as prophylaxis for recurrent herpes meningitis 1, 4.

All patients with viral meningitis should be assessed by an infection or neurological specialist 1, 5.