Lance-Adams Syndrome in the Pretargeted Temperature Management Era

Abstract

Acute posthypoxic myoclonus portends a poor prognosis. Another form of posthypoxic myoclonus, Lance-Adams syndrome, is associated with a better outcome. Differentiating these two entities is important in prognostication and guiding further medical intervention. This can be difficult in the acute setting after hypoxic brain injury but the use of neurophysiologic studies may be helpful. In this article, we present a case of a patient who presented after pulseless electrical activity arrest, underwent targeted temperature management and subsequently developed Lance-Adams syndrome. The neurologic and electroencephalographic findings in Lance-Adams syndrome are discussed with an updated review.

Myoclonus after Cardiac Arrest: Where Do We Go from Here?

“…Multiple studies have demonstrated that these EEG patterns, as well as others that signify severe brain injury, predict worse outcomes when found in those with PHM after CRA (4,5,21,(24)(25)(26)29). This was also described in a review by Gupta et al that included 37 articles, of which a number are included in this review (4,11,12,24,27,29, and a number of cases of LAS also described in Freund et al [3]). Other studies have demonstrated the importance of malignant EEG patterns in determining poor prognosis in early PHM but failed to include patients with PHM and more benign neurophysiological findings for comparison (6,11,12,15,17).…”

“…However, a more recent study has demonstrated that localization based on the clinical exam is not consistent (4). Though studies have used neurophysiological testing to determine the origin of subtypes of PHM (3,27,35), they have been flawed due to the inconsistent use of EEG-EMG polygraphy and somatosensory evoked potentials (SSEP), both of which have been shown to be the most reliable means of diagnosing cortical myoclonus (3). Therefore, defining cortical and subcortical myoclonus using neurophysiological studies in evaluating early PHM needs further study.…”

“…Early or "acute" PHM, or MSE, has been differentiated from "chronic" PHM, or Lance-Adams syndrome (LAS), which has been defined as PHM occurring after the acute post-arrest period and portends a better outcome (3). However, cases of chronic PHM may occur within 5 to 8 hours of CRA, therefore making the distinction by time-of-onset less helpful, particularly acutely after CRA (3,5,23). The delay in diagnosing some cases of LAS is confounded by the use of sedatives to facilitate ventilator-assisted breathing shortly after CRA, which might mask LAS (3,23,31).…”

“…However, cases of chronic PHM may occur within 5 to 8 hours of CRA, therefore making the distinction by time-of-onset less helpful, particularly acutely after CRA (3,5,23). The delay in diagnosing some cases of LAS is confounded by the use of sedatives to facilitate ventilator-assisted breathing shortly after CRA, which might mask LAS (3,23,31). As a result, patients may be diagnosed with MSE when in fact they have LAS (3,5,20), leading to false diagnosis and inaccurate prognostication.…”

“…One particular examination finding of prognostic importance is early posthypoxic myoclonus (PHM). Early PHM is defined clinically by focal, multifocal, or generalized myoclonic movements of the face, trunk, extremities, and sternocleidomastoid and trapezius muscles that begin within 72 hours of CRA (3)(4)(5)(6)(7)(8). Early PHM arises due to brain injury and subsequent increased neuronal hyperactivity (3,5,6).…”