Anesthetic Management of Hashimoto's Encephalopathy Presenting for Spine Surgery
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.329609
Source of Support: None, Conflict of Interest: None
Keywords: Hashimoto's encephalopathy, neurosurgery, neuroanesthesia
Hashimoto's encephalopathy (HE) is a neuroendocrine disorder with a relapsing and remitting course and is also known as steroid-responsive encephalopathy associated with autoimmune thyroiditis or nonvasculitic autoimmune meningoencephalitis., It is a rare disorder, and there are no reports regarding anesthetic implications in a patient diagnosed with HE.
A 38-year-old female presented with complaints of low backache for the past ten years with difficulty in walking for the past year. A diagnosis of L4-S1 intervertebral disc prolapse was made, and she was posted for L4 -S1 discectomy. The patient gave history of multiple episodes of loss of consciousness, followed by seizures, and was diagnosed with HE with thyroiditis 3 months back and was on steroids, antiepileptic medications, and thyroxine. On examination, the patient had a Glasgow coma scale was 15. Examination of the central nervous system revealed a motor power of 4/5 on bilateral lower limbs. Airway examination revealed a Mallampati grade III with limited neck extension and a pretracheal swelling 2 × 3 cm with deviation of trachea to the right. Thyroid function tests revealed subclinical hypothyroidism with elevated TSH and normal T3 and T4 levels and patient was on oral thyroxine 75 mg and oral prednisolone 10 mg. Electrocardiogram (ECG) showed bradycardia and delayed the progression of the R wave. Echocardiogram revealed grade I diastolic dysfunction. Blood investigation revealed moderate levels of antithyroid antibodies and antialpha enolase antibodies. The cerebrospinal fluid analysis done 3 months back showed albumin cytological dissociation with high level of proteins. Preoperative pulmonary function test, electroencephalography, serum electrolytes, coagulation profile, and renal function were within normal limits. After consultation with neurosurgeons, we decided to proceed with the surgery as the patient had features of spinal cord compression which warranted an urgent decompression.
On the day of surgery, after attaching standard monitors like five lead ECG, noninvasive blood pressure monitoring, and pulse oximetry, the patient was induced with thiopentone sodium 5 mg·kg-1, fentanyl 2 μg·kg-1, and vecuronium 0.1 mg·kg-1 to facilitate tracheal intubation. The airway was secured with a 7.5 cuffed reinforced endotracheal tube aided by the C-MAC video laryngoscope; the left radial artery was cannulated for a beat to beat monitoring of the blood pressure, and a peripherally inserted central line was secured through the left cubital vein. Baseline arterial blood gas was within normal limits. The patient was placed in prone position keeping the head and neck in a neutral position. Anesthesia was maintained with total intravenous anesthesia to facilitate intraoperative neuromonitoring with motor-evoked potential, free run electromyography, and direct nerve stimulation (DES) with propofol (100–200 μg·kg-1·h-1) and fentanyl 1 μg·kg-1·h-1. Intraoperative steroid replacement was done with hydrocortisone 100 mg. Bispectral index (BIS) monitoring was done to optimize the depth of anesthesia with a target BIS of 40, and forced-air warmer was used to maintain normothermia. The mean blood pressure was maintained between 70 and 80 mmHg and EtCO2 between 35 and 40 mmHg. The surgery lasted for 4 h with a urine output of 800 mL and blood loss 300 mL which was within the allowable blood loss limit. At the end of the surgery, after assessment of neurological status, the patient was extubated and shifted to intensive care unit (ICU).
Postoperatively, the patient was monitored in the ICU for 48 h with specific attention to the neurological status. The oral thyroxine, prednisolone, and antiepileptic medications were restarted from the day 1 of the postoperative period and was discharged home on the fourth postoperative day.
HE is an encephalopathy of presumed autoimmune origin characterized by high titere of antithyroid peroxidase antibodies. Patients with HE are known to be associated with rheumatoid arthritis, pernicious anemia, Myasthenia gravis, Addison's disease, systemic lupus erythematosus, and ulcerative colitis. Hence, preanesthetic evaluation must be meticulously done to rule out such disorders. A long-standing goitre can result in tracheal compression or deviation thereby resulting in a difficult airway scenario. The possibility of tracheomalacia should be considered during induction and extubation. Preoperative thyroid function test will determine the adequacy of treatment and aid to optimize the thyroid hormone therapy. Elective surgery is postponed until patient is euthyroid. Patients with HE and hypothyroidism may have abnormal coagulation cascade, due to reduced factor VIII and acquired von Willebrand's disease which may get unmasked during a surgical procedure., Hence, evaluation of preoperative coagulation profile is necessary.
Patients with HE can have a plethora of systemic manifestations. These patients may have an unusual response to Valsalva maneuver due to hypothyroidism-induced baroreceptor defect., Autonomic dysfunction can result in hypotensive episodes during induction of anesthesia, prone positioning, and intraoperative Valsalva maneuver. The peripheral nervous system may be affected, presenting as peripheral polyneuropathy and entrapment neuropathies such as a carpal tunnel or Guyone canal syndromes making these patients prone for nerve injuries during intraoperative positioning. Renal dysfunction is encountered in this patients due to increased systemic vascular resistance, decreased renal perfusion, increased antidiuretic hormone, decreased atrial natriuretic factor, and reduced activity of the renin-angiotensin-aldosterone system. Close monitoring of renal function and avoidance of nephrotoxic drugs will prevent worsening of the renal function in the perioperative period.
HE with hypothyroidism is associated with obstructive sleep apnea, which can result in delayed extubation, prolonged mechanical ventilation, and affect the postoperative outcome., Upper airway obstruction may manifest due to increased tongue size and obesity which is commonly encountered in this subset of patients. They are also prone for aspiration pneumonia and postoperative ileus due to reduced gastrointestinal motility, and esophageal sphincter dysfunction. Postoperative pain management regimens with opioids should be used cautiously in view of upper airway obstruction and increased risk of aspiration.
Perioperative HE presents as a subacute or acute onset of altered sensorium with or without seizures. HE is associated with myoclonus or tremulousness and frequent episodes of transient ischemic attacks. Patients are prone for relapse during the perioperative period causing delayed recovery in the postoperative period. When HE is suspected, a bedside EEG and evaluating antithyroid antibody levels will help in diagnosis. However, there is no correlation between the amount of antibody levels and the presence or severity of symptoms. Patients with HE respond well to steroid therapy and will be on oral prednisolone therapy depending on the clinical course of the disease. Hence, it is essential to continue the steroid therapy and antiepileptic therapy in the perioperative period.
HE is a unique clinical scenario because of its rarity, variety of presentations, and a high incidence of misdiagnosis. A meticulous preoperative assessment and balanced anesthesia is essential to reduce the perioperative morbidity. Awareness of the clinical condition and extreme vigilance can detect relapses in the perioperative period.
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