Transient shivering during Wada test provides insight into human thermoregulation

Abstract

SUMMARYPurpose: Some patients with pharmacoresistant epilepsy undergoing the Wada test experience transient shivering. The purpose of this study was to investigate various clinical and radiographic characteristics of these individuals to delineate underlying mechanisms of this phenomenon. Methods: A systematic review of prospectively collected information on patients undergoing the Wada test was performed. All demographic, clinical, and radiographic information was obtained and reviewed by the appropriate expert in the field; statistical analysis was performed to determine the predictors of transient shivering. Results: A total of 120 consecutive carotid artery injections in 59 patients were included in the study. Shivering was observed in 46% of the patients, and it was not significantly affected by gender, age, location of epileptogenic zone, brain lesion on magnetic resonance imaging (MRI), side of the first injection, duration of the hemiparesis, or excess slow wave activity on electroencephalography (EEG). However, shivering was more likely to follow sodium amobarbital injection if there was no filling of the posterior circulation on cerebral angiogram. Resective epilepsy surgery is performed in patients with medically intractable localization-related epilepsy to control or eliminate their seizures (Engel et al., 2003). This involves surgical removal of the epileptogenic zone, and it frequently includes unilateral temporal lobe resection. Some patients undergo the intracarotid amobarbital procedure (IAP) or Wada test, performed by injecting sodium amobarbital into each internal carotid artery separately, thereby anesthetizing and creating a temporary functional lesion of the brain perfused by that circulation. We have observed transient shivering in some patients during the Wada test. The relationship of shivering in the context of this test has not been delineated. Therefore, in this study, we attempt to attain further understanding regarding this clinical phenomenon.In mammals, the hypothalamus is known to be critically involved in thermoregulation. Shivering is part of the thermoregulation process and is quickly activated if the organism is exposed to cold temperature. We also know that although the branches originating from the anterior circulation perfuse the anterior hypothalamus, the branches from the posterior circulation perfuse the posterior aspect of the hypothalamus (Haymaker, 1969). We hypothesize that the transient ''functional lesion'' of part of the hypothalamus induced by the sodium amobarbital injection is responsible for temporary shivering. MethodsThe IAP is performed as part of the presurgical workup for patients with pharmacoresistant epilepsy to evaluate language dominance and functional memory reserve of the contralateral temporal lobe. At our institution, a team of a neuroradiologist, a neurologist, and a neuropsychologist performs the test. The neuroradiologist introduces a catheter

Clinical significance and developmental changes of auditory-language-related gamma activity

“…Thirty-one patients underwent a Wada test (Shah et al, 2010; Kojima et al, 2012). Left-hemispheric language dominance was suggested in 26 patients and bilateral language representation was suggested in 2 patients.…”

The contribution of posterior circulation to memory function during the intracarotid amobarbital procedure

“…To the best of our knowledge, memory function during IAP has never been assessed in relation to the presence or absence of an FTP. In a recent study the presence or absence of an FTP was related to transient shivering during IAP and thermoregulation of the thalamus [13]. Memory function was not addressed in this previous study.…”

Intracarotid Etomidate is a Safe Alternative to Sodium Amobarbital for the Wada Test

“…Because of this, in some centers, sodium amytal was prewarmed routinely before injection. However, Shah et al 23 have reported that shivering was more likely to follow sodium amobarbital injection if there was no filling of the posterior circulation on a cerebral angiogram. They postulated that a transient but selective functional lesion of the anterior hypothalamus produced by the effects of sodium amobarbital may result in disinhibition of the posterior hypothalamus and other brainstem thermoregulatory centers, thereby inducing transient shivering.…”

“…They postulated that a transient but selective functional lesion of the anterior hypothalamus produced by the effects of sodium amobarbital may result in disinhibition of the posterior hypothalamus and other brainstem thermoregulatory centers, thereby inducing transient shivering. 23 Transient mood changes were observed infrequently during the procedure. In our study, 3 patients became very restless and agitated, especially after the second injection, needing sedation to calm them; several others showed less drastic effects involving sobbing or laughter.…”

“…One study quotes 46% incidence of transient shivering with amobarbital. 23 The exact mechanism of shivering is not known. One of the postulated mechanisms was that shivering may be caused by the injection of cold drug into the brain, activating cold responses from the hypothalamus.…”