What are the symptoms of Primary Amoebic Meningoencephalitis (PAM) caused by Naegleria fowleri?

Symptoms of Primary Amoebic Meningoencephalitis (PAM)

Primary Amoebic Meningoencephalitis (PAM) presents with symptoms that mimic bacterial meningitis but does not respond to standard antibiotic therapy, leading to death due to cerebral edema typically within 5 days of presentation if untreated. 1

Initial Symptoms (First 1-3 Days)

• Change in taste or smell occurring 2-5 days after swimming in warm freshwater 1
• Fever (present in 94.9% of cases) 2
• Severe headache (present in 71.8% of cases) 2
• Nausea and vomiting (present in 69.2% of cases) 2
• Stiff neck 1
• Photophobia (sensitivity to light) 1

Progressive Symptoms (Days 3-5)

• Meningismus (signs of meningeal irritation) 1
• Papilledema (swelling of the optic disc) 1
• Nystagmus (involuntary eye movement) 1
• Cranial nerve abnormalities 1
• Ataxia (lack of muscle coordination) 1
• Altered mental status/confusion 2
• Seizures (present in 25.6% of cases) 2
• Abnormal behavior 1

Terminal Stage Symptoms

• Rapid neurological deterioration 1
• Hemiparesis (weakness on one side of the body) 1
• Loss of balance and body control 3
• Coma 3
• Death due to cerebral edema 1

Laboratory Findings

• CSF analysis resembling bacterial meningitis 2:
  • Neutrophilic pleocytosis (median 3000 cells/μL) 2
  • Low glucose levels (median 14 mg/dL) 2
  • Elevated protein levels (median 344 mg/dL) 2

Imaging Findings

• Abnormal imaging in approximately 75% of patients 2
• Cerebral edema (66.7% of cases) 2
• Hydrocephalus (25.6% of cases) 2
• Cerebral infarctions (12.8% of cases) 2

Risk Factors and Exposure History

• Swimming in warm freshwater lakes or rivers, particularly during summer months 1
• Use of neti pots or nasal irrigation with untreated water 1
• Ritual nasal ablution 1
• Playing on lawn water slides connected to municipal water supplies 1

Important Clinical Considerations

• PAM has an extremely high mortality rate exceeding 95% 1, 4
• The disease progresses very rapidly, with death typically occurring within 5 days of presentation if untreated 1
• Pre-mortem diagnosis is confirmed in only 27% of cases 1
• PAM should be included in the differential diagnosis for any patient with rapidly progressive meningoencephalitis following water exposure or nasal lavage 4
• Early diagnosis and immediate treatment initiation with a multi-drug regimen including amphotericin B and miltefosine are critical for survival 4, 5