What is the diagnosis for chronic meningitis presenting as dementia?

From the Guidelines

Chronic meningitis can indeed present as dementia, particularly in elderly patients, and requires prompt diagnosis and treatment to prevent permanent neurological damage or death. This occurs when persistent inflammation of the meninges (the protective membranes covering the brain and spinal cord) leads to cognitive decline, memory problems, and behavioral changes that mimic dementia. The most common causes include fungal infections (cryptococcosis, histoplasmosis), tuberculosis, syphilis, Lyme disease, and certain cancers 1. Diagnosis requires a high index of suspicion, especially when dementia symptoms progress rapidly or are accompanied by headache, low-grade fever, or subtle neurological deficits. A lumbar puncture is essential, typically showing elevated protein, low glucose, and pleocytosis in the cerebrospinal fluid.

Some key considerations for diagnosis and management include:

• The likelihood of any specific aetiology depends on a range of factors, including age, immune status, and exposure history 1
• In many cases (34%-74%), no pathogen is identified, highlighting the importance of empirical treatment and further investigation 1
• Treatment depends on the underlying cause: antifungals like amphotericin B (initial dose 0.7-1.0 mg/kg/day) followed by fluconazole (400-800 mg daily for 8-10 weeks, then 200 mg daily for maintenance) for fungal causes; anti-tuberculosis therapy (isoniazid 5 mg/kg/day, rifampin 10 mg/kg/day, pyrazinamide 15-30 mg/kg/day, and ethambutol 15-25 mg/kg/day for 2 months, followed by isoniazid and rifampin for 7-10 months) for TB meningitis; or penicillin G (18-24 million units daily for 10-14 days) for neurosyphilis.
• Early treatment is crucial as cognitive impairment may be partially or completely reversible if the underlying infection is treated promptly, whereas delayed diagnosis can lead to permanent neurological damage or death 1.

It is also important to distinguish between infectious encephalitis and postinfectious or postimmunization encephalitis or encephalomyelitis, as the management approach is different 1. Encephalitis should also be distinguished from encephalopathy (e.g., secondary to metabolic disturbances, hypoxia, ischemia, drugs, intoxications, organ dysfunction, or systemic infections), which is defined by a disruption of brain function in the absence of a direct inflammatory process in the brain parenchyma 1.

From the Research

Chronic Meningitis Presenting as Dementia

• Chronic meningitis can present with a wide range of symptoms, including cognitive impairment and dementia 2, 3.
• The differential diagnosis for chronic meningitis is broad and encompasses autoimmune, neoplastic, and infectious etiologies 4, 5.
• Cognitive impairments, including dementia, can present as first symptoms at the acute stage, and/or as sequelae in the chronic stages, in some patients with bacterial meningitis or encephalitides 2.
• Suitable therapeutic management of these diseases at the acute stage is required in order to avoid these sequelae 2.
• Chronic meningitis is defined as inflammation involving the meninges that lasts at least 4 weeks and is associated with a CSF pleocytosis 5.
• The etiology of chronic meningitis remains challenging, with no cause identified in at least one-third of cases 3, 5.

Diagnostic Approach

• A multifaceted approach that combines history, physical examination, neuroimaging, and laboratory analysis, including novel diagnostic platforms, is needed to diagnose chronic meningitis 5.
• Identification of the etiology of chronic meningitis requires assembling a multidisciplinary team of individuals, including those with specialized expertise in ophthalmology, dermatology, rheumatology, and infectious diseases 5.
• Several serologic, CSF, and neuroimaging studies are indicated, although novel diagnostic platforms including metagenomic deep sequencing may hold promise for identifying organisms 5.

Treatment and Outcome

• Infectious etiologies are more common in those at risk for disseminated disease, specifically those who are immunocompromised 5.
• Most patients with idiopathic chronic meningitis have a relatively good outcome 3.
• Suitable therapeutic management of chronic meningitis is crucial to avoid sequelae, including cognitive impairment and dementia 2.