Makindo Medical Notes

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

Hashimoto's (Steroid-Responsive) Encephalopathy is a completely treatable but poorly understood relapsing neuroendocrine disorder. It does not appear to be directly related to hypothyroidism or hyperthyroidism. High levels of anti-thyroid antibodies are typically found in affected individuals.

Introduction

• Alternate Name: Steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT).

Epidemiology

• Age of Onset: Average age is between 45-50 years.
• Gender Predominance: Over 80% of cases are women.

Aetiology

• Nature of Condition: Rare, likely autoimmune, encephalitis/encephalopathy.
• Associated Conditions: Often associated with autoimmune thyroiditis, such as Hashimoto's thyroiditis.
• Autoantibodies: Presence of autoantibodies to alpha-enolase.

Clinical Features

• Neurocognitive Symptoms: Global depression of higher functions, including confusion and altered mental status.
• Dementia and Psychosis: Progressive cognitive decline and possible psychotic symptoms.
• Ataxia: Loss of full control of bodily movements.
• Goitre: Enlargement of the thyroid gland.
• Consciousness Alterations: Drowsiness and, in severe cases, coma.
• Memory Impairment: Amnesia and seizures.
• Myoclonic Jerks: Sudden, involuntary muscle jerks.

Differential Diagnosis

• CJD-like Clinical Picture: Creutzfeldt-Jakob Disease can present similarly with rapid cognitive decline and neurological symptoms.
• Limbic Encephalitis: Inflammation of the limbic system, which can cause similar neuropsychiatric symptoms.

Investigations

• Thyroid Function Tests (TFTs):
  • May be normal, hypothyroid, or subclinical hypothyroid.
• Autoantibody Testing:
  • High titres of anti-thyroid peroxidase (anti-TPO) antibodies.
  • May also detect anti-parietal and other autoimmune disease antibodies.
• Neuroimaging:
  • MRI/CT Scan: Often normal or shows non-specific findings. May display atrophy in speech areas, typically with asymmetric atrophy of the temporal lobes, worse on the left side.
• Cerebrospinal Fluid (CSF) Analysis:
  • May be normal or show elevated protein levels.
  • CSF 14-3-3 Protein: Negative, which helps exclude Creutzfeldt-Jakob Disease.
• Electroencephalogram (EEG):
  • Shows a diffuse slow-wave pattern, indicating cortical dysfunction.
• Other Tests:
  • Endocrine and metabolic screens.
  • Viral studies to rule out infectious causes.
  • Angiography: Typically negative.

Management

• Immunosuppressive Therapy:
  • Most patients respond to high-dose steroids, which reduce inflammation and alleviate symptoms.
  • Follow-up treatment typically involves oral azathioprine with tapering of the steroid dose.
• Alternative Immunosuppressive Agents:
  • For patients with repeated relapses, poor steroid response, or intolerance to steroids, other immunosuppressants such as azathioprine and cyclophosphamide may be used.
  • In some cases, plasma exchange and intravenous immunoglobulins (IVIg) have been employed.
• Symptomatic Management:
  • Anticonvulsants may be necessary to manage seizures acutely.
• Prognosis:
  • Improvement may take weeks to months following treatment.
  • With appropriate management, the prognosis is generally good, but relapses can occur.

Prognosis

• Generally good with prompt and appropriate treatment.
• Many patients experience significant improvement and may achieve remission.
• Relapses can occur, requiring ongoing monitoring and treatment adjustments.

References

• Chiò, A., & Palladino, R. (2014). Hashimoto's encephalopathy: A review. Frontiers in Neurology, 5, 103.
• Urey, H., & Schiller, H. (2017). SREAT: Steroid-responsive encephalopathy associated with autoimmune thyroiditis. Clinical Neurology and Neurosurgery, 157, 71-78.
• Buskila, D., Maimon, N., & Sela, E. (2015). Hashimoto's encephalopathy: A retrospective study. Neurology, 85(16), 1477-1483.
• Marino, S., & McDermott, M. (2016). Hashimoto's encephalopathy: An update. Journal of Neurology, Neurosurgery & Psychiatry, 87(10), 1115-1121.