Chapter 5. Adverse Effects - Adverse Effects of ECT

Written by Juli Lawrence

Third, patients vary considerably in the extent and severity of cognitive side effects following ECT. There is limited information about the factors that contribute to these individual differences. There is evidence that among depressed patients without known neurological disease or insult, the extent of preECT global cognitive impairment, i.e., mini-Mental State Exam (MMSE) scores, predicts the magnitude of retrograde amnesia for autobiographical information at long-term follow-up. While ECT typically results in improvement in global cognitive status in these patients, as a function of symptomatic response, nonetheless, these same patients may have greater persistent amnesia for personal memories (Sobin et al. 1995). Similarly, there is evidence that the duration of disorientation immediately following the ECT treatment is independently predictive of the magnitude of retrograde amnesia for autobiographical information. Patients who require prolonged periods to recover orientation may be at greater risk for more profound and persistent retrograde amnesia (Sobin et al. 1995). Patients with pre-existing neurological disease or insult (e.g., Parkinson's disease, stroke) may also be at increased risk for ECT-induced delirium and memory deficits (Figiel et al. 1991). Magnetic resonance imaging (MRI) findings of basal ganglia lesions and severe white matter hyperintensities have also been linked to the development of an ECT-induced delirium (Figiel et al. 1990). Some medications may exacerbate ECT-induced cognitive side effects. These include lithium carbonate (Small et al. 1980; Weiner et al. 1980b), and medications with marked anticholinergic, properties, particularly in elderly patients.

Fourth, ECT results in highly characteristic cognitive changes. Across diagnostic groups, prior to receiving ECT, many patients have deficits in attention and concentration that limit their capacity information (Byrne 1977; Pogue-Geile and Oltmanns, 1980; Cornblatt et al. 1981; Sackeim and Steif, 1988). For example, patients with severe psychopathology often have deficient recall of information that was just presented to them (immediate memory). In depressed patients, these deficits are most marked for unstructured material that requires effortful processing in order to impose organization (Weingartner and Silberman 1984; Roy-Byrne et al. 1986). However, such patients are considerably less likely to have deficits in retaining the new information that they do learn (delayed memory) (Cronholm and Ottosson 1961; Sternberg and Jarvik 1976; Steif et al. 1986). With symptomatic response following ECT, the deficits in attention and concentration usually resolve. Consequently, measures of immediate memory are either unchanged or improved within a few days of ECT termination (Cronholm and Ottosson, 1961; Steif et al. 1986; Weiner et al. 1986b; Rossi et al. 1990; Sackeim et al. 1993). Since attention and concentration are essential to many aspects of cognitive function, it is not surprising that shortly following completion of the ECT course improvement may be observed in a wide variety of neuropsychological domains, including global cognitive status (Sackeim et al. 1991; Sobin et al. 1995) and measures of general intelligence (IQ) (Huston and Strother 1948; Stieper et al 1951; Squire et al. 1975; Malloy et al. 1981; Sackeim et al. 1992). There is no evidence that ECT results in impairments of executive functions (e.g., the capacity to shift mental sets), abstract reasoning, creativity, semantic memory, implicit memory, or skill acquisition or retention (Weeks et al. 1980; Frith et al. 1983; Squire et al. 1984; Taylor and Abrams 1985; Jones et al. 1988).

Against this background of unchanged or improved neuropsychological performance, ECT selectively results in anterograde and retrograde amnesia. The anterograde amnesia is characterized by rapid forgetting of newly-learned information (Cronholm and Ottosson 1961; Squire 1986; Steif et al. 1986; Weiner et al. 1986b; Frith et al. 1987; Sackeim et al. 1993). As noted, compared to preECT baseline, a few days following ECT patients may recall more items in a list that was just presented. However, recall after a delay will often be impaired (Korin et al. 1956; Cronholm and Ottosson 1961; Cronholm and Molander 1964; Squire and Miller 1974; Steif et al. 1986; Weiner et al. Squire and Chace 1975; d'Elia 1976; Robertson and Inglis 1978, 1986b; Calev et al. 1989b; Sackeim et al. 1993). The extent and persistence of this rapid forgetting of newly learned information varies among patients and should be taken into account when making recommendations regarding the postECT convalescence period. Until there is substantial resolution of the anterograde amnesia, returning to work, making important financial or personal decisions, or driving may be restricted. The anterograde amnesia rapidly resolves following the termination of ECT. Indeed, no study has documented anterograde amnestic effects of ECT more than a few weeks following the ECT course (Strain et al. 1968; Bidder et al. 1970; Heshe et al. 1978; Jackson, 1978; Fraser and Glass, 1980; Weeks et al. 1980; Gangadhar et al. 1982; Frith et al. 1983; Weiner et al. 1986b; Sackeim et al. 1993). It is unlikely that ECT has any long-term effect on the capacity to learn and retain new information.

Following ECT, patients also display retrograde amnesia. Deficits in the recall of both personal (autobiographical) and public information are usually evident, and the deficits are typically greatest for events that occurred temporally closest to the treatment (Janis, 1950; Cronholm and Molander 1961; Strain et al. 1968; Squire 1975; Squire et al. 1975, 1976, 1981; Weeks et al. 1980; Sackeim et al. 1986; Wiener et al 1986b; Sackeim et al 1993; McElhiney et al. 1995). The magnitude of the retrograde amnesia is greatest immediately following the treatment. A few days following the ECT course, memory for events in the remote past is usually intact, but there may be difficulty in recalling events that transpired several months to years prior to ECT. The retrograde amnesia over this time span is rarely complete. Rather, patients have gaps or spottiness in their memories of personal and public events. Recent evidence suggests that the retrograde amnesia is typically greater for public information (knowledge of events in the world) as compared to personal information (autobiographic details of the patient's life) (Lisanby et al. in press). The emotional valence of autobiographical events, i.e., memories of pleasant or distressful events, is not related to their likelihood of being forgotten (McElhiney et al. 1995).

As time from ECT increases, there is usually substantial reduction in the extent of retrograde amnesia. Older memories are more likely to be recovered. The time course for this shrinkage of retrograde amnesia is often more gradual than that for the resolution of anterograde amnesia. In many patients the recovery from retrograde amnesia will be incomplete, and there is evidence that ECT can result in persistent or permanent memory loss (Squire et al. 1981; Weiner et al. 1986b; McElhiney et al. 1995; Sobin et al. 1995). Owing to a combination of anterograde and retrograde effects, many patients may manifest persistent loss of memory for some events that transpired in the interval starting several months before and extending to several weeks following the ECT course. There are individual differences, however, and, uncommonly, some patients may experience persistent amnesia that extends back several years prior to ECT. Profound and persistent retrograde amnesia may be more likely in patients with pre-existing neurological impairment and patients who receive large numbers of treatments, using methods that accentuate acute cognitive side effects (e.g., sine wave stimulation, bilateral electrode placement, high electrical stimulus intensity).

To determine the occurrence and severity of cognitive changes during and following the ECT course, orientation and memory functions should be assessed prior to initiation of ECT and throughout the course of treatment (see Chapter 12 for details).