Eosinophilic meningitis (EM)
presents a diagnostic challenge due to its varied etiologies,
encompassing both infectious and non-infectious causes.
Typically, cerebrospinal fluid (CSF) devoid of eosinophils
serves as the norm, with their presence indicating a potential
underlying condition such as parasitic infections or other
systemic disorders.
Eosinophilic meningitis is defined as presence of 10 or more
eosinophils per microliter in CSF or eosinophils constituting
at least 10% of total CSF leucocyte count [1]. Infection with
helminthic parasites is considered as the most common source.
Other infectious agents include fungi, bacteria, rickettsiae
and viruses. Non-infectious causes of EM include malignancy
like Hodgkins lymphoma, Non-Hodgkins lymphoma, eosinophilic
leukemia, medications like Ciprofloxacin, Ibuprofen,
Vancomycin and systemic diseases like sarcoidosis,and
hypereosinophilic syndrome.
Predominant infectious agents include Angiostrongyliasis,
Gnathostomiasis, Neurocysticercosis, cerebral Toxocariasis and
Schistosomiasis. Among these Angiostrongyliasis stands out as
the most prevalent cause, notably affecting regions like
South-East Asia, the Pacific basin, and the Caribbean [2].
Human infection typically stems from the ingestion of raw
intermediate hosts such as snails or crustaceans harboring
larvae.
3 types of presentation include headache, encephalitis, ocular
manifestations like retinal detachment which occurs when
larvae migrates to the eyes.
Clinical features develop 2-35 days after ingestion of larvae
with the most common symptom being headache [3]. Fever maybe
present only in less than 50% of cases. Associated
neurological findings include radiculopathies, cranial nerve
palsies and cognitive dysfunction. Neck stiffness is seen in
50% of cases. A high clinical suspicion along with CSF
eosinophilia should strongly suggest the possibility of
eosinophilic meningitis (EM). At least 2/3rd of patients have
peripheral blood eosinophilia [4]. Specific immunodiagnosis
maybe done by Western Blot analysis.
A. cantonenensis meninigitis is differentiated from
other helminthic infections of the central nervous system by
the characteristic absence of focal lesions on brain imaging
[2]. Treatment is usually supportive. Anti helminthic
treatment can often worsen symptoms due to inflammatory
reaction to antigens [4]. A short course of steroids is found
to relieve headache [5]. Symptoms usually resolve completely
by 3-6 weeks.
EM due to Gnathostomiasis is more fulminant [6]. It reaches
CNS by migrating along nerve roots. As with the case of
Angiostronglyiasis, this parasite is also endemic throughout
Southeast Asia [7]. The larvae enter humans by consumption of
raw fish or poultry. Radiculitis is the most distinctive
clinical manifestation of
G. spinigerum infection
[6]. Other clinical manifestations include cranial nerve
palsies, myelitis or intermittent subcutaneous migratory
swelling. CSF shows xanthochromia and brain imaging shows
scattered multiple focal lesions. Similar to
Angiostrongyliasis, treatment here is also supportive.
Fungal eosinophilic meningitis by
Coccidioides Immitis
is one of the most common causes of EM in the US [6].
Meningitis is seen in 50% of patients with disseminated
disease. Similar to parasitic infection, CSF eosniophilia is a
prominent finding in coccidiodal meningitis [8]. Rarely,
eosinophilic meningitis has been reported in bacterial
infections like Tuberculous meningitis [1] and neurosyphilis.
Various hematological malignancies have been associated with
CSF eosinophilia, most common being Hodgkin's disease [9].
Other malignancies associated with EM include acute
Lymphoblastic leukemia, T-lineage non Hodgkin's lymphoma,
chronic eosinophilic leukemia, and disseminated glioblastoma.
CSF eosinophilia is also associated with use of certain drugs
like ibuprofen, ciprofloxacin, intraventricular vancomycin
[10] and gentamycin.
In this issue of the
Journal, Karadan U et al has
presented an interesting case of eosinophilic meningitis
presenting as atypical lumbosacral meningitis. In addition,
the patient also had severe and persistent headache with
features of raised intracranial pressure [11].
In conclusion, while EM remains a rare entity, its diverse
etiologies necessitate a high index of suspicion among
clinicians encountering patients with unexplained neurological
symptoms. Vigilance in recognizing CSF eosinophilia coupled
with a comprehensive understanding of potential underlying
causes is paramount in achieving timely diagnosis and
effective management of this challenging condition.
References
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Eosinophilic Enigma: Deciphering Intriguing Symptomatology and
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BMH Med. J. 2024; 11(3):49-51.