Makindo Medical Notes.com

Related Subjects: |Anti-NMDA (NMDAR) receptor encephalitis |Herpes Simplex Encephalitis (HSV) |Acute Encephalitis |Limbic Encephalitis |Paraneoplastic Limbic Encephalitis (Dementia) |Hashimoto's (Steroid responsive) Encephalopathy |Acute Disseminated Encephalomyelitis

Limbic encephalitis (LE) is an inflammatory condition primarily affecting the limbic system, which includes structures such as the hippocampus, amygdala, and cingulate gyrus. This condition often presents with a rapid onset of cognitive, behavioural, and neurological symptoms.

About

• A rare but potentially treatable cause of delirium

Types

• Paraneoplastic Limbic Encephalitis: Associated with underlying malignancies, such as small cell lung cancer, testicular tumours, or thymoma. This type is often linked to autoantibodies against neuronal antigens (e.g., anti-Hu, anti-Ma2, anti-CRMP5).
• Non-Paraneoplastic Limbic Encephalitis: Often autoimmune in nature, associated with antibodies such as anti-NMDA receptor, anti-VGKC (voltage-gated potassium channel), or anti-GAD (glutamic acid decarboxylase).
• Infectious Causes: Viral encephalitis (e.g., herpes simplex virus) can also lead to inflammation of the limbic system.

Clinical

• Acute delirium. speech difficulties, myoclonic jerks
• Inattention, weakness, seizures, bizarre behaviour
• Psychiatric type syndromes, amnestic deficits
• REM associated sleep defects (VGKC Ab Limbic encephalitis)

Differentials

• Paraneoplastic syndrome
• Encephalitis (infective or autoimmune)
• Lewy-body dementia
• Prion disease
• Lupus cerebritis
• Toxic and metabolic encephalopathies
• Multiple sclerosis
• Hashimoto's encephalopathy
• Wernicke's encephalopathy
• Neurosyphilis,
• Primary vasculitis of the central nervous system
• Leptomeningeal involvement of malignancy

Investigations

• FBC, U&E, LFT, CRP, CXR: hyponatraemia (VGKC Ab Limbic encephalitis)
• Imaging: CT Brain may be normal. Needs MRI to show hyperintense signals on T2-weighted or fluid-attenuated inversion recovery (FLAIR) sequences, atrophic temporal-limbic structures on T1 weighted images usually of temporal lobes and hippocampus. Hyperintensity in the medial temporal lobes on T2-weighted or FLAIR sequences.
• EEG: may show slow wave activity or epileptiform activity often in the temporal lobes
• CSF: protein and WCC may be elevated. CSF Protein 14-3-3 negative. Oligoclonal bands. Specific antibody testing can be crucial. Voltage-gated potassium channel antibodies: high titres > 400pmol/L
• CT and PET scans Chest Abdomen Pelvis for malignancy
• Malignancy associated autoantibodies: Hu, Ma2, Ovarian teratoma (Anti NMDA)

Management

• Autoimmune disease: Treatment is through immunosuppression in autoimmune limbic encephalitis. Usually, Plasma-exchange, corticosteroids and IVIG are all recommended. A trial of steroids may be considered when infection is excluded. A dramatic response may be seen with VGKC ab positive disease
• Second-line treatments may include rituximab or cyclophosphamide
• Antiviral Therapy: where related to viral infections, such as herpes simplex virus, appropriate antiviral therapy is indicated.
• Paraneoplastic: Management of underlying tumour as possible. Limited responses to immunotherapy.
• Anti-seizure medications, psychiatric care, and cognitive rehabilitation may be necessary for managing symptoms

References