Amebic Meningoencephalitis Clinical Presentation

Updated: Oct 12, 2021
  • Author: Linda Nguyen, MD; Chief Editor: Russell W Steele, MD  more...
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The history seldom helps to differentiate amebic meningoencephalitis from other CNS diseases.

Primary amebic meningoencephalitis

 Characteristics of PAM are as follows:

  • PAM commonly affects children and young adults who have previously been healthy

  • This disease occurs more often during the warmer months of the year and in warmer climates

  • Patients with PAM typically have a history of swimming, diving, bathing, or playing in warm, generally stagnant, freshwater during the previous 1-9 days

  • Rarely, patients with PAM may experience disordered smell or taste

  • Most often, the symptoms of PAM are indistinguishable from those of acute bacterial meningitis.

  • The acute onset of PAM occurs over a period of hours to 1-2 days

Granulomatous amebic encephalitis

 The characteristics of GAE include the following:

  • It affects individuals of all ages, although those at the extremes of age may be more susceptible

  • Persons with debility or immunocompromise may be more susceptible to GAE

  • There is no seasonal variation because the causative pathogens are ubiquitous

  • Individuals with GAE may have keratoconjunctivitis or a skin ulcer or lesion preceding neurologic symptoms

  • A subacute or chronic presentation lasting days or weeks


General Presentation

The presentation of primary amebic meningoencephalitis closely mimics that of bacterial meningitis. Patients typically present with fever, headache, nausea, vomiting, photophobia, and stiff neck. [22] Additional symptoms include confusion, somnolence, seizures, and coma. In all cases reported to date, there has been a history of water entry into the nose. [23] Symptom onset begins 1-9 days after such an exposure. [24]

Typical symptoms of GAE include low-grade fever and focal neurologic signs, such as cranial nerve palsies, hemiplegia, ataxia, aphasia, diplopia, and seizures. Patients with GAE may also exhibit behavioral changes, stiff neck, signs of increasing intracranial pressure (ICP), stupor, or coma. Symptom onset ranges from weeks to months after exposure. Interestingly, cases of Balamuthia have been reported with patients’ skin lesions occurring months to years prior to the onset of neurologic manifestations. [25]


Physical Examination

Physical examination seldom helps to differentiate amebic meningoencephalitis from other CNS diseases.

Primary amebic meningoencephalitis

Patients may uncommonly experience abnormal smell or taste. Typical signs include high fever, photophobia, stiff neck, mental status change, and seizures. PAM may progress rapidly to cerebral herniation secondary to increased intracranial pressure. Rarely, myocarditis may occur, although amoebae are not present in the myocardium on histologic evaluation.

Granulomatous amebic encephalitis

Individuals with GAE may have low-grade fever, photophobia, and/or stiff neck. Focal neurologic findings, such as cranial nerve palsies, hemiplegias, aphasias, ataxias, or diplopia, are observed more commonly. When present, seizures may be focal or generalized. Later in the disease course, GAE patients may demonstrate signs of elevated ICP and cerebral herniation. Keratoconjunctivitis, primarily in people who wear contact lenses, or skin lesions may rarely predate neurologic signs and symptoms.