Abstract

Introduction: Hashimoto’s encephalopathy, also known as steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT), is a rare autoimmune condition characterized by neuropsychiatric symptoms and elevated antithyroid antibody levels. Its clinical presentation is highly variable and may include diffuse or focal central nervous system involvement, typically evolving in a subacute, relapsing–remitting pattern. We report the case of a patient diagnosed with SREAT at our institution, whose condition was revealed by continuous segmental motor phenomena of the right hemibody upon awakening. Case description: This is the case of a 45-year-old female patient with no known pathological history, who woke up in the morning with segmental motor symptoms on the right side and a speech arrest. She was admitted six hours after the onset of symptoms for management of functional impairment of the right hemibody, associated with a speech disorder. Neurological examination revealed right flaccid hemiparesis, predominantly affecting the right arm and face, ataxia of the right hand with the phenomenon of a wayward parietal hand, and Broca’s aphasia. A cerebral CT angiography was performed, followed by a brain MRI angiography, which revealed cortico-subcortical inflammatory-like lesions in the left fronto-parieto-temporal region, bilateral thalami, and caudate nuclei. Cerebrospinal fluid (CSF) analysis showed a mild increase in protein levels (0.7 g/L), normal cytology, absence of oligoclonal bands, and no intrathecal synthesis. Twelve hours after the initial symptoms, the patient developed focal status epilepticus, which was treated with phenobarbital, leading to recovery of speech but persistence of motor symptoms. Thyroid antibodies were highly positive (antithyroid peroxidase antibodies at 771 IU/mL, anti-thyroglobulin antibodies at 615 IU/L), along with a positive antinuclear antibody (ANA) titer (1:320). Given the signs of encephalitis associated with autoimmune thyroiditis and after ruling out other differential diagnoses, a diagnosis of Hashimoto’s encephalopathy was made. The patient received intravenous methylprednisolone (1g/day) for three days, followed by an oral dose of 60 mg/day with adjunctive therapy. After six days of corticosteroid treatment with unsatisfactory improvement (persistence of motor symptoms), intravenous immunoglobulin (IVIG) therapy was initiated at a dose of 2 g/kg over five days, without adverse effects. The clinical condition improved dramatically, with complete resolution of motor symptoms after three days. The patient developed a Cushingoid appearance on oral corticosteroids (60 mg/day) with a 5 kg weight gain, but no clinical relapse. This led to the introduction of azathioprine (2 mg/kg/day) and a gradual tapering of corticosteroids to 20 mg/day over six weeks. After 10 months of follow-up, the patient exhibited attention and concentration difficulties, but no relapse or motor sequelae. Conclusion: Steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT) is a rare autoimmune neuroendocrine disorder with heterogeneous clinical presentation. This condition should be suspected in any case of acute or subacute motor symptoms associated with a focal status epilepticus as the initial manifestation. Early diagnosis and appropriate treatment can prevent irreversible complications. Intravenous immunoglobulin (IVIG) therapy is a valuable alternative in cases showing poor response to glucocorticoids.

Keywords

steroid-responsive encephalopathy associated with autoimmune thyroiditis, hashimoto’s encephalopathy, anti-thyroglobulin antibodies, anti-thyroperoxidase antibodies, intravenous immunoglobulin, ischemic stroke, focal status epilepticus