|Year : 2014 | Volume
| Issue : 3 | Page : 133-135
Steroid responsive myoclonus as a presentation of Hashimoto's encephalopathy
Rajeev Philip, Sanjay Saran, Manish Gutch, Arya Tungveersingh
Department of Endocrinology, Lala Lajpat Rai Memorial Medical College, Meerut, Uttar Pradesh, India
|Date of Web Publication||13-Aug-2014|
G 10, PG Hostel, Lala Lajpat Rai Memorial Medical College, Meerut 250 004, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
Hashimoto's Encephalopathy (HE) can have highly variable neuropsychiatric manifestations, making it difficult to diagnose, and may go unrecognized for a long time. HE is a diagnosis of exclusion and should be kept in mind when evaluating a patient with cognitive dysfunction and high titres of antithyroid antibodies as it responds dramatically to steroids. Steroid responsive myoclonus can be a presentation of HE.
Keywords: Antithyroid antibodies, autoimmune thyroid disease, Hashimoto encephalopathy, hypothyroidism, steroid responsive encephalopathy
|How to cite this article:|
Philip R, Saran S, Gutch M, Tungveersingh A. Steroid responsive myoclonus as a presentation of Hashimoto's encephalopathy. Thyroid Res Pract 2014;11:133-5
|How to cite this URL:|
Philip R, Saran S, Gutch M, Tungveersingh A. Steroid responsive myoclonus as a presentation of Hashimoto's encephalopathy. Thyroid Res Pract [serial online] 2014 [cited 2020 Jul 16];11:133-5. Available from: http://www.thetrp.net/text.asp?2014/11/3/133/138563
| Introduction|| |
Hashimoto's encephalopathy (HE) is a rare steroid responsive encephalopathy syndrome characterised by persisting or fluctuating neurologic and neuropsychologic deficits associated with elevated blood concentrations of antithyroid antibodies.  Even though the presence of antithyroid antibodies is essential to make a diagnosis of HE, these antibodies does not appear to be the cause of the disease and appear to be a marker of the disease.  The classically described clinical manifestations usually include acute to subacute onset of confusion with alteration of consciousness, but myoclonus is a less publicized manifestation of the disease.  We present a case of HE, presenting as steroid responsive myoclonus in a setting of autoimmune thyroid disease.
| Case report|| |
An 18-year-old gentleman was diagnosed to have primary hypothyroidism six months back following weight gain, edema and facial puffiness of 3 years duration [Figure 1]. His initial thyroid function test (TFT) was T4: 2.3 μg/dl (5.01-12.4) T3: 0.35 ng/ml (0.6-1.81), and TSH: 180 μiu/ml (0.35-5.50) and was started on L thyroxine, with significant improvement of symptoms. He started developing myoclonus for the past one month and had two episodes of generalized tonic clonic seizures, for which he was referred to our hospital.
On examination he was conscious, with cognitive impairment. He had memory loss for recent events, with poor attention span, difficulty in finding words, dyscalculia, and dysgraphia. His Mini mental status examination (MMSE) was 11, suggestive of moderate cognitive impairment. He also had myoclonus, involving both upper limbs and lower limbs.
On investigations, blood routine examination and ESR was normal, and Liver Function test, Kidney Function Test, sodium, potassium, calcium and magnesium were normal, and so were the arterial blood gas analysis. His latest TFTs showed normal T3 and T4 with mild elevation of TSH (TSH-9.1 μiu/ml). Antithyroid peroxidase antibody was positive (>1300 IU ml). His Electroencephalography (EEG) showed diffuse slow wave activity [Figure 2] and Magnetic resonance images (MRI) showed pituitary hyperplasia [Figure 3] with non-specific white matter changes [Figure 4]. Cerebrospinal Fluid Studies (CSF) study had normal cytology, but slightly increased protein.
|Figure 4: Magnetic resonance image brain showing non-specific white matter changes|
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Antinuclear antibody titter, anti-double-stranded DNA, hepatitis B surface antigen, anti-hepatitis C virus, lupus anticoagulant and VDRL were done to evaluate the cause of decreased cognitive function, myoclonus and seizures, which were all negative. CSF electrophoresis was normal.
In view of these neurologic symptoms, associated with high titers of antithyroid antibodies and the exclusion of other possible causes of encephalopathy, the patient was diagnosed with HE. He was started on methylprednisolone 1 g/day for 3 days, and was shifted over to prednisone 1 mg/kg/day. There was a marked improvement in the symptoms with no further episodes of myoclonus or seizures. One month after discharge, the patient reported a sustained improvement on all parameters, including memory and cognition, making it possible for him to return to an almost normal routine. His MMSE had improved to 26 and he is seizure free. Prednisone dose was tapped over the period of 3 months without the recurrence of symptoms.
| Discussion|| |
HE is a rare steroid responsive neuropsychiatric syndrome, associated with serologic evidence of antithyroid antibodies, when other causes of encephalopathy are excluded. This syndrome was first described by Brain et al., in 1966,  but it still remains a rare or under diagnosed condition with only about 130 cases reported in literature till date, predominantly in adult females. The difficulty in diagnosis is due to the varied presentations and subtlety of symptoms which may be acute or chronic. 
The pathophysiology of HE is still unclear and the proposed pathogenetic mechanisms include autoimmune cerebral vasculitis, toxic effects of thyroid-stimulating hormone on the CNS and neuronal reaction mediated by antibodies. Out of these, the autoimmune mechanisms seem to be the most likely reason.  Even though the presence of elevated serum levels of antithyroid antibodies remain an essential characteristic of HE diagnosis, the antibodies does not appear to be pathogenic, and are considered as markers of the disease. Based on this observation, it has been proposed to rename HE as Steroid-responsive encephalopathy associated with autoimmune thyroiditis, (SREAT). 
The clinical manifestations usually include acute to sub-acute onset of confusion with alteration of consciousness. Two major patterns of presentations were described: 25% of patients follow a stroke-like pattern of multiple recurrent episodes of focal neurologic deficits with a variable degree of cognitive dysfunction and consciousness impairment; and the remaining 75% present with a diffuse progressive pattern of slow cognitive decline with dementia, confusion and hallucinations. Two-thirds of patients may experience focal or generalized tonic-clonic seizures, and 12% may be present with status epileptics. Hyperreflexia and other pyramidal tract signs are found in 85% of patients; and psychosis, visual hallucinations and paranoid delusions have been reported in 25% to 36% of patients. ,
Myoclonus is a less publicized but common manifestation of HE, with 52% patients diagnosed to have HE, having history of myoclonus. 
The diagnosis of HE should be considered in patients presenting with the characteristic neuropsychiatric manifestations excluding other causes of encephalopathy. They should have (1) Presence of high levels of antithyroid antibodies in serum or CSF; (2) no alteration in the CSF and/or imaging tests compatible with infectious, vascular, or neoplastic etiology; and (3) a good response to immunosuppressive therapy.
Elevated CSF protein is a common, but not an essential feature.  The thyroid profile may be variable, with 23% to 35% of patients having subclinical hypothyroidism, 17% to 20% having hypothyroidism, 7% having hyperthyroidism, and 18% to 45% being euthyroid.
Non-specific EEG abnormalities are seen in 90% to 98% of patients, which is usually a non-specific slow background activity. Focal spikes or sharp waves and transient epileptic activity are less common.  Brain computed tomography or MRI showed abnormalities in 49% of patients such as cerebral atrophy, focal cortical abnormality, diffuse subcortical abnormality and non-specific subcortical focal white matter abnormality. 
The disease is responsive to immunosuppressive therapy and IV methylprednisolone (500-1,000 mg/day) for 3 to 5 days, followed by a oral dose of prednisone (1-2 mg/kg/day), which is followed by gradual tapering based on clinical response being the commonly followed protocol. Around 2-5% of patients may not respond to steroids, in whom azathioprine, IV Immunoglobulins, or plasmapharesis can be used with good results. 
Hashimoto's encephalopathy is a rare steroid responsive encephalopathy associated with positive anti thyroid antibodies. The manifestations are highly variable, making it difficult to diagnose. Steroid responsive myoclonus can be a rare manifestation of this disease.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]