What are the presentation, diagnostic work‑up, and management of mumps‑associated meningoencephalitis?

Mumps-Associated Meningoencephalitis: Presentation, Diagnosis, and Management

Clinical Presentation

Mumps meningoencephalitis presents with fever (90-97%), vomiting (90-94%), and headache (65-88.8%), but critically, parotitis is present in only 50% of cases at the time of CNS involvement. 1, 2, 3

Key Clinical Features to Assess:

• Meningeal signs: Neck stiffness and photophobia occur in approximately 70% of cases 2
• Mental status changes: Rapid deterioration in consciousness level distinguishes encephalitis from isolated meningitis 4, 5
• Seizures: Present in 30% of mumps meningoencephalitis cases 2
• Focal neurological deficits: Including cranial nerve palsies, paralysis, or movement disorders 6, 7
• Parotid swelling: Absence does NOT exclude mumps—15-20% of mumps infections are completely asymptomatic and up to 50% present without parotitis 8, 9

Critical Timing Considerations:

• CNS complications can occur without preceding parotitis 3, 7
• Patients are contagious from 7 days before through 8 days after parotitis onset 6
• Vaccine-associated cases (Urabe strain, not used in US) can occur 19-26 days post-vaccination 2

Diagnostic Work-Up

Laboratory confirmation is strongly preferred over clinical diagnosis alone, as only 30-40% of mumps infections produce typical parotitis and multiple other conditions can mimic this presentation. 8

Essential CSF Analysis:

• Cell count: Mean 513-540/mm³ with lymphocyte predominance (mean lymphocytes 300/mm³) 1, 2
• Protein: Mean 56.97 mg/dL; levels >40 mg/dL in 55% of cases 1, 2
• Glucose: Mean 53.67 mg/dL with CSF/blood glucose ratio >0.4 in all cases (mean 0.53) 1, 2
• PCR testing: CSF should be tested for mumps virus, enteroviruses, HSV-1, HSV-2, and VZV by PCR 4

Confirmatory Laboratory Testing:

• Isolation of mumps virus from clinical specimens (CSF, throat swab, or urine) 6, 8
• Serologic testing: Positive mumps IgM antibody or significant rise in serum mumps IgG antibody 6, 8
• Stool and/or throat swabs for viral PCR 4

Neuroimaging:

• MRI is preferred over CT for superior resolution when intracranial abnormalities are suspected 4
• Specific findings: Discrete lesions in brainstem, thalamus, and bilateral hippocampal involvement have been documented 5, 3
• Indications: Obtain imaging for focal neurologic deficits, seizures, altered mental status, or signs of increased intracranial pressure 4

Additional Diagnostic Considerations:

• EEG: May be indicated in selected cases with seizures or persistent altered consciousness 4
• Repeated lumbar puncture: NOT routinely indicated as yield is limited 4

Management

Treatment consists exclusively of supportive care with strict isolation precautions for 5 days after parotitis onset, as there is no specific antiviral therapy for mumps meningoencephalitis. 6, 8, 9

Immediate Supportive Care:

• Pain and fever control: Acetaminophen or NSAIDs for fever, headache, and parotid pain 6, 8, 9
• Hydration: Ensure adequate fluid intake, as parotitis makes swallowing uncomfortable 6, 9
• Nutrition: Soft foods and avoidance of acidic foods that stimulate salivary flow 6, 9

Mandatory Isolation Measures:

• Implement droplet precautions immediately and isolate for 5 days after parotitis onset 6, 8, 9
• Report cases immediately to state and local health departments 6, 8, 9
• Educate patients and families about transmission through respiratory droplets and direct contact with saliva 6

Monitoring for Severe Complications:

Adults require heightened surveillance as complications are significantly more common and severe than in children. 6, 8, 9

• Hearing loss: Assess for sudden sensorineural deafness, which can be bilateral and permanent 6, 9
• Seizure management: Standard anticonvulsant therapy if seizures occur 4
• Increased intracranial pressure: Monitor for signs requiring neurosurgical intervention 4
• Hydrocephalus: Placement of external ventricular drain if obstructive hydrocephalus develops 4

Specific Interventions for Complications:

• Facial nerve palsy: If facial droop or weakness develops, initiate prednisone 1-2 mg/kg/day for 5-7 days followed by taper over 5-7 days 6, 8, 9
• Eye protection: Provide corneal protection if facial weakness prevents complete eye closure 6, 8, 9

Prognosis and Recovery:

• Most patients recover without intervention beyond supportive care 9, 1
• Mean hospitalization: 5.1 days (longer in males and with higher CSF protein or lower CSF/blood glucose ratio) 1
• Complete recovery: Occurs in approximately 70-80% of facial nerve palsy cases within 3-6 months 9
• Mortality: Extremely rare in mumps meningoencephalitis 1

Critical Pitfalls to Avoid:

• Do NOT delay isolation while awaiting laboratory confirmation—implement droplet precautions immediately based on clinical suspicion 6, 8
• Do NOT exclude mumps based on absence of parotitis—CNS complications can occur without parotid involvement 3, 7
• Do NOT assume immunity based on vaccination history alone—recent outbreaks have occurred in highly vaccinated populations, particularly in institutional settings 9, 5
• Do NOT administer mumps vaccine to pregnant women due to theoretical risk from live-virus vaccine 6, 8, 9
• Do NOT routinely repeat lumbar puncture as diagnostic yield is limited 4

Special Population Considerations:

• Pregnancy: Treatment follows same supportive care principles; mumps infection in first trimester increases risk for fetal death but is NOT associated with congenital malformations 6, 8
• Institutional outbreaks: Identify and vaccinate susceptible contacts immediately; exclude susceptible individuals until vaccinated or 26 days after last case 6