Article, Neurology

Neurologic and neuropsychological symptoms during the first year after an electric shock: results of a prospective multicenter study

Original Contribution

Neurologic and neuropsychological symptoms during the first year after an electric shock: results of a prospective multicenter study?

Benoit Bailey MD, MSca,b,c,?, Pierre Gaudreault MDb,c, Robert L. Thivierge MDc

aDivision of Emergency Medicine, CHU Ste-Justine, Montreal, Quebec, Canada H3T 1C5

bDivision of Clinical Pharmacology and Toxicology, CHU Ste-Justine, Montreal, Quebec, Canada H3T 1C5

cDepartment of Pediatrics, CHU Ste-Justine, Montreal, Quebec, Canada H3T 1C5

Received 12 May 2007; revised 22 June 2007; accepted 28 June 2007

Abstract

Objectives: To assess the prevalence of neurologic and neuropsychological symptoms in the short-term and 1 year after an electric shock and to explore whether any of these were associated with risk factors. Methods: Patients presenting to one of 21 EDs between October 2000 and November 2004 were eligible to be enrolled in a prospective observational study after an electric shock if they had risk factors for late arrhythmias. telephone follow-up was done to evaluate the appearance of symptoms.

Results: A total of 30 (26%) of 114 patients complained of neurologic or neuropsychological symptoms at a median of 52 days post-electric shock. At 1 year, 24 (28%) of 86 patients complained of neurologic or neuropsychological symptoms. None of the risk factors evaluated were associated with the symptoms.

Conclusion: The prevalence of the symptoms we observed should alarm all emergency physicians that the effect of electricity can cause late neurologic and neuropsychological manifestations.

(C) 2008

Introduction

Electrical injury can directly affect many systems and virtually no organ is protected against it [1]. Indirect injuries related to electric shock-induced trauma such as fall or projection can also be seen. Despite the fact that burns and

? This study was supported by a grant from Hydro-Quebec.

* Corresponding author. CHU Ste-Justine, Montreal, Quebec, Canada H3T 1C5. Tel.: +1 514 345 4931×6276; fax: +1 514 345 4823.

E-mail address: [email protected] (B. Bailey).

Cardiac manifestations are the most recognized injuries after an electric shock, central and Peripheral nervous system injuries both directly or indirectly are significant and frequent [2-4]. Also, less recognized in emergency medicine is the possibility of neuroPsychological effects caused by the electrical injury [3-6]. Some patients may show various emotional and behavioral sequelae, but also Memory loss and symptoms of depression [3-5].

The purpose of the present study was to assess the prevalence of neurologic and neuropsychological symptoms at short-term and 1 year after an Electrical shock that was severe enough to require 24 hours cardiac monitoring and to explore whether any of the symptoms were associated with

0735-6757/$ – see front matter (C) 2008 doi:10.1016/j.ajem.2007.06.021

certain risk factors. The cardiac manifestations in this group of patients were previously described [7].

Methods

All patients presenting to one of 21 participating EDs (Appendix A) from October 2000 to November 2004 were eligible to be enrolled in a prospective observational study after an electrical shock if they required cardiac monitoring because they had at least one risk factor and if they gave their consent. These risk factors are transthoracic current, tetany longer than 1 second, lost of consciousness of any length, or voltage source of 1000 V or more. Exclusion criteria were patients who refused consent to the study or patients with an injury not caused by an electric shock. The EDs covered a wide geographic area and ranged from small community hospitals to Tertiary care centers, including pediatric hospitals, with a median annual census of 37000 (range, 20000-85000).

Once ED physicians determined the eligibility and obtained signed consent, they completed a standardized form with details concerning the electric shock. The standardized form contained the following items: age, sex, time of accident and assessment in the ED, scenario of the accident including voltage and source of the electricity, and with the presence or not of the following factors: tetany, transthoracic current, loss of consciousness, wet extremities, and burns. Patients were called by a research nurse at least 1 month after the electric shock and 1 year later to determine whether they had any neurologic or neuropsychological symptoms since their discharge from the ED. A standardized form was used by the research nurse and contained both open and specific questions: need for scheduled or unscheduled medical visit since discharge, any health concerns, and any numbness, tingling, or pain of the extremities, generalized weakness, muscular weakness, and depression.

Table 1 Voltage involved in the electric shock among the 134 patients enrolled in the study

The difference in the rate of symptoms according to the voltage category was evaluated either by ?2 or Fisher exact test, whenever appropriate (SPSS version 13.0, Chicago, Ill). The difference in the prevalence of risk factors between patients with normal follow-up vs those with neurologic or neuropsychological symptoms at the short-term or the 1-year follow-up was evaluated by ?2 or Fisher exact test, whenever appropriate (SPSS version 13.0). In all cases, when significant, the difference and its 95% confidence interval were reported. Also, a correlation with the initial Creatine phosphokinase levels and the presence of neurologic or neuropsychological symptoms at the short-term or the 1-year follow-up was done by Spearman’s ? (SPSS version 13.0).

All data were entered onto an Excel spreadsheet (Microsoft, Redmond, Wash) by the research nurse. The entries were verified by the principal investigator. Missing data were completed by consulting the original charts of the

patients obtained by the hospital medical charts office. The study was approved by each hospital’s institutional review board. In the case of primary care hospitals without institutional review board, the study was approved by the physician-in-chief of the hospital and by the principal investigator’s institutional review board. For children, parental consent was obtained.

Results

Over the 4-year period, 134 patients aged 29.8 +-

16.1 years including 26 children were recruited. There were 88 work-related accidents.

The voltage that the patients were exposed to is presented in Table 1. Most of the exposure occurred with domestic or industrial voltages. The incidence of the factors that made the patients eligible in the study and of other potential risk factors is presented in Table 2. Most of the patients had only 1 risk factor. The size of the burns was estimated at a median of 1 cm2 (n = 57, range 0.09-16). The degree of the burns was first in 32 patients, second in 28, third in 5, and unspecified in 12. A total of 115 patients had normal initial and discharge Electrocardiograms [7]. Of the 15 patients who had an abnormal or borderline initial ECG, 8 were unchanged at discharge. Four patients had abnormal or borderline initial ECGs that normalized completely at discharge. There were 4 patients with normal initial ECGs but borderline discharge ECGs [7]. Cardiac monitoring was done up to 23.8 +- 6.7 hours post-electric shock. Except for the anomalies noted on the discharge ECGs, cardiac monitoring was normal in all but 2 patients: one patient developed a long PR that lasted 12 hours (up to

Voltage (V)

No. of patients (%)

Domestic

120

42

(31)

240

22

(16)

Industrial

347

20

(15)

460

1

(1)

600

29

(22)

1200

1

(1)

Distribution

4000

3

(2)

5000

1

(1)

14400

4

(3)

25000

3

(2)

52000

1

(1)

DC

750

1

(1%)

Unknown

6

(4)

Factors n (%)

Transthoracic current 105 (78)

Tetany N1 s 54 (40)

Loss of consciousness 7 (5)

Voltage source >=1000 V 13 (10)

Humid or wet 22 (16)

Burn marks 77 (57)

Abnormal initial ECG 19 (14)

240 milliseconds) and another had a P-wave block with an atrial extrasystole.

Table 2 Prevalence of the risk factors in the patients enrolled in the study

At the short-term follow-up done at a mean of 72.2 +-

54.6 days (median, 52) post-electric shock, 30 (26%) of 114 patients complained of new neurologic or neuropsy- chological symptoms. These symptoms are presented in Table 3. Only 5 patients (17%) consulted specifically for these symptoms at the time of the follow-up. There was no difference in the rate of symptoms according to the category of voltage (domestic, industrial, and distribution). At the 1-year follow-up done at a mean of 397 +- 54.6 days (median, 392) post-electric shock, 24 (28%) of 86 patients complained of neurologic or neuropsychological symptoms. Late symptoms appeared after the short-term follow-up in 12 patients, whereas 12 were already sympto- matic at the short-term follow-up. These symptoms are presented in Table 4. There was no difference in the rate of

Table 3 Neurologic and neuropsychological symptoms mentioned at the short-term telephone follow-up a

Symptoms

Domestic (n = 54)

Industrial (n = 44)

Distribution (n = 12)

Total b

(n = 114)

General

5

(9)

6 (14)

1

(8)

14 (12)

weakness–

fatigue

Pain

4

(7)

6 (14)

2

(17)

12 (10)

Muscular

2

(4)

5 (11)

0

8 (7)

weakness

Extremity

1

(2)

5 (11)

1

(8)

7 (6)

tingling

Extremity

1

(2)

4 (9)

0

5 (4)

numbness

Headaches

3

(6)

1 (2)

0

5 (4)

Memory loss

0

3 (7)

0

3 (3)

Psychologic

2

(4)

0

0

2 (2)

symptoms

Dizziness

1

(2)

1 (2)

0

2 (2)

Depression

0

0

1

(8)

1 (1)

Gait imbalance

1

(2)

0

0

1 (1)

Values are shown as n (%).

a There was no statistical difference in the rate of symptoms according to the voltage category.

b Includes unknown voltage and 750 DC.

symptoms according to the category of voltage (domestic, industrial, and distribution).

Table 4 Neurologic and neuropsychological symptoms mentioned at the 1-year telephone follow-up a

Symptoms

Domestic (n = 36)

Industrial (n = 37)

Distribution (n = 10)

Total b (n = 86)

Muscular

1 (3)

5 (14)

1

(10)

8 (9)

weakness

Extremity

2 (6)

5 (14)

0

8 (9)

numbness

Pain

2 (6)

4 (11)

1

(10)

7 (8)

General

3 (8)

1 (3)

1

(10)

6 (7)

weakness–

fatigue

Depression

3 (8)

2 (5)

1

(10)

6 (7)

Extremity

2 (6)

3 (8)

0

5 (6)

tingling

Memory loss

0

2 (5)

0

2 (2)

Psychological

0

0

1

(10)

1 (1)

symptoms

Dizziness

1 (3)

0

0

1 (1)

Values are shown as n (%).

a There was no statistical difference in the rate of symptoms according to the voltage category.

b Includes unknown voltage and 750 DC.

There were no more significant risk factors in patients with neurologic or neuropsychological symptoms compared to normal follow-up either at short-term or at 1 year, although wet or humid extremities almost reached statistical sig-

nificance at the short-term follow-up (?14.8%, 95% CI -0.4 to 33.3) (Tables 5 and 6). The same can be said about burn marks at the 1-year follow-up (?27%, 95% CI -3.6 to 46.6) (Table 6).

Creatine phosphokinase was measured in 116 patients a median of 2.5 hours post-electric shock: 264 +- 658 U/L (median 163, range 45-7110). There was no correlation between the initial CPK level and the presence of neurologic or neuropsychological symptoms at the short-term follow-up (rs = -0.05, P = 1.0) and at the 1-year follow-up (rs = -0.20, P = .09).

Discussion

The sequelae of electrical injuries can be immediate and either transient or prolonged and permanent or delayed and progressive [8]. Delayed and progressive symptoms are particularly difficult to diagnose because the link between the injury and the symptoms can often go unrecognized by the patients and also by their physicians. Neurologic and neuropsychological manifestations after an electrical shock have received some attention in the literature as illustrated by a recent article that reviewed the neurologic and neuropsy- chological assessments in 29 studies and in another article that presents results of a web-based interactive survey [3,9].

Table 5 Prevalence of risk factors in patients with normal follow-up and in patients with neurologic or neuropsychological symptoms at the short-term follow-up a

Transthoracic current

Tetany

Loss of consciousness

Voltage N1000 V

Wet or humid

Burn marks

Abnormal ECG

Normal

64/84 (76)

34/84 (40)

4/84 (5)

10/84 (12)

10/84 (12)

36/84 (43)

11/84 (13)

Symptomatic

25/30 (83)

14/30 (47)

2/30 (7)

2/30 (7)

8/30 (27)

15/30 (50)

6/30 (20)

Values are shown as n (%).

a There was no statistical difference in the prevalence of risk factors between patients with normal follow-up vs those with neurologic or neuropsychological symptoms.

Not much, however, has been written in the emergency medicine literature.

In our cohort, more than a quarter of the patients who experienced an electric shock severe enough to require cardiac monitoring complained of neurologic or neuropsy- chological symptoms 2 months after the injuries and 1 year later. The immediate, secondary, and late effects of electric shock on the nervous system have been well described for the first time in 1964 in a review of 14 cases exposed to voltage from 220 to 44000 V [10]. Late effects concern cerebral, basal ganglia, Cranial nerves, brain stem, spinal cord, peripheral nerve lesions, and autonomic nervous system manifestations in addition to what has been called functional effects that can now be more accurately described as neuropsychological effects [10]. Secondary effects concern temporary paralysis, muscular pain in the trunk and extremities, autonomic disturbances, and head- ache that usually disappear within the first week but may also persist for a longer period [10]. In a retrospective study of 90 patients, 11 (50%) of 22 patients with low-voltage injuries presented with neurological symptoms in which

2 (18%) of 11 persisted [2]. In the high-voltage group, 4 (19%) of 21 patients with no neurologic deficits at the time of admission developed symptoms later [2]. Among the patients who had momentary loss of consciousness, 6 (30%) of 20 had persistent or developed delayed central neuropathy [2]. Also, 11 patients developed symptoms of delayed neuropathy such as muscle weakness, sensory deficit, paresthesias, and new pain in the absence of symptoms initially [2].

The cause of the neurologic and neuropsychological symptoms after an electrical shock is unclear. The damage

caused by the heat generated by the current does not explain all symptoms especially those related to the central nervous system. Tissue damage can also result from cellular rupture induced by the presence of an electric field or what is called electroporation [3]. It has also been suggested that it could be secondary to diffuse Cerebral injury [11]. In fact, several authors have noticed similarities between victims of electrical injuries and of head trauma [9]. Mild nonfocal neuropsychological symptoms such as memory loss or attention deficit and other symptoms such as headaches, fatigue, or depression are present in both populations [9]. The difference in the sequelae among patients with electrical injuries may be due to the difference in the electrical contact similar to the differences seen in mechanism in head trauma [9].

In our study, no risk factors that we studied were associated with the presence of symptoms at the short-term follow-up and 1 year later. In a study of 73 adults after an electrical injury, it was reported that tetany and Altered level of consciousness were associated with a diagnosis of major

depression (?28%, 95% CI 3-48 and ?28%, 95% CI 0.8-49, respectively); and that loss of consciousness and altered level

of consciousness were associated with posttraumatic stress disorder (?30%, 95% CI 2-52 and ?32%, 95% CI 4-52,

respectively) 3 months to 9 years post-electrical injury [12].

When we look only at depression, none of the risk factors were associated with it in our study. The difference between the study by Kelley et al [12] and ours may well be explained by the selection of patients. In the study by Kelley et al, the cohort consisted of patients consulting for neurocognitive and psychiatric evaluations after their electric injury, whereas our cohort consisted of those

Table 6 Prevalence of risk factors in patients with normal follow-up and in patients with neurologic or neuropsychological symptoms at the 1-year follow-up a

Transthoracic current

Tetany

Loss of consciousness

Voltage N1000 V

Wet or humid

Burn marks

Abnormal ECG

Normal

45/62 (73)

27/62 (44)

4/62 (6)

8/62 (13)

9/62 (14)

22/62 (36)

8/62 (13)

Symptomatic

18/24 (75)

10/24 (43)

3/24 (12)

3/24 (12)

5/24 (21)

15/24 (62)

4/24 (17)

Values are shown as n (%).

a There was no statistical difference in the prevalence of risk factors between patients with normal follow-up vs those with neurologic or neuropsychological symptoms.

who were initially asymptomatic but were observed only for the purpose of cardiac monitoring [12]. In addition, we only studied complaints by the patients not the clinical diagnosis as was the case in the Kelley et al [12] study. However, other studies have found no correlation between the neuropsychological complaints and the severity of the injury [3,11]. There was no correlation between the initial CPK levels and the presence of neurologic or neuropsychological symptoms at follow-up despite the fact that the degree of muscle tissue injury corresponds to the initial CPK levels in victims of high voltage (N1000) injuries [13]. This reinforces the notion that the damage caused by the heat generated by the current does not explain all symptoms and that other mechanisms as discussed previously are involved.

Limitations to the study include the fact that patients with symptoms were not examined by us because of the vast Geographical area covered by our study. The same can be said about asymptomatic patients. However, our study tried to address an important issue in a cohort of patients with theoretical risk factors for arrhythmias. Future study on electrical injuries should include long-term evaluation for both cardiac and neurologic and neuropsychological symptoms [7]. Another limitation is the number of patients lost to follow-up, especially at the 1-year follow-up. Also, because only patients with theoretical risk factors for arrhythmias were included, this does not represent the whole spectrum of the injury.

Because we are not sure what were the clinical diagnoses behind the complaints reported by the victims, we cannot be certain of the causes. Despite this, the prevalence of the symptoms we observed should alarm all emergency physicians that the effect of electricity can cause late neurologic and neuropsychological manifestations and incapacitate the patient long after their discharge from the ED. Patients should receive counseling on this issue before they leave the ED. Should the need arise, follow-up should be ensured in the same manner as with patients treated with head trauma.

Acknowledgments

All participating centers and in particular the site investigators: Dr Yves Rouleau and Dr Laurent Vanier (Hopital Charles-Lemoyne), Dr Benoit Laflamme (Hopital Pierre-Boucher), Dr Nadine Cassiani (Hopital Maisonneuve- Rosemont), Dr Chantal Guimont (CHUQ-CHUL), Dr Serge Brouillet (CHRDL), Dr Dominic Chalut (MUHC-Montreal Children Hospital), Dr J Scott Delaney and Dr Robert Primavesi (MUHC-Montreal General/Royal Victoria), Dr Marc Boulet (CHUM-Pavillon Notre-Dame), Dr Pierre Desaulniers (CHUM-Pavillon Hotel-Dieu), Dr Christian Geadah (CH Regional de Sept-Iles), Dr Catherine Begin (CH Regional de Rimouski), Dr Sylvain Blanchet (Reseau de

Sante du Temiscouata), Dr Stephane Poulin (CH Lauren- tien), Dr Daniel Rousseau (CH Lachine), Dr Pierre Gosselin (CLSC-Centre de Sante des Sept-Rivieres), Dr Tom Vandor (Hopital Barrie Memorial), Dr Louis Belanger (RSSS des Aurores Boreales), Dr Annie Charbonneau (CH-CHSLD Matane), and Dr Jean-Levy Paquette (CHCR-Antoine- Labelle). Catherine Guimond and Catherine Lamoureux our research nurses. Dr Guy Riendeau and Dr Michel Plante of Hydro-Quebec. Dr Barbara Cummins-McManus for reviewing the manuscript.

Appendix A. Participating centers

Tertiary care pediatric hospitals

CHU Ste-Justine

MUHC-Montreal Children Hospital Tertiary care adult hospitals Hopital Maisonneuve-Rosemont MUHC-Royal-Victoria

MUHC-Montreal General CHUQ-CHUL

CHUM-Pavillon Notre-Dame CHUM-Pavillon Hotel-Dieu Regional hospitals

Hopital Charles-Lemoyne Hopital Pierre-Boucher CH Regional de Sept-Iles CH Regional de Rimouski

Centre Hospitalier Regional de Lanaudiere

Primary care hospitals

Reseau de sante du Temiscouata CH Laurentien

CH Lachine

CLSC-Centre de Sante des Sept-Rivieres Hopital Barrie Memorial

RSSS des Aurores Boreales CH-CHSLD Matane CHCR-Antoine-Labelle

References

  1. Koumbourlis AC. Electrical injuries. Crit Care Med 2002;30:S424-30.
  2. Grube BJ, Heimbach D, Engrav LH, Copass MK. Neurologic consequences of electrical burns. J Trauma 1990;30:254-8.
  3. Morse MS, Berg JS, TenWolde RL. Diffuse electrical injury: a study of 89 subjects reporting long-term symptomatology that is remote to the theoretical current pathway. IEEE Trans Biomed Eng 2004;51: 1449-59.
  4. Yarnell P, Lammertse D. Neurorehabilitation of lightning and electrical injuries. Sem Neurol 1995;15:391-6.
  5. Martin T, Salvatore NF, Johnstone B. cognitive decline over time following electrical injury. Brain Inj 2003;17:817-23.
  6. Hooshmand H, Radfar F, Beckner E. The neurophysiological aspects of electrical injuries. Clin Encephal 1989;20:111-20.
  7. Bailey B, Gaudreault P, Thivierge RL. Cardiac monitoring of high-risk patients after an electrical injury: a prospective multicentre study. Emerg Med J 2007;24:348-52.
  8. Cherington M. Central nervous system complications of lightning and electrical injuries. Sem Neurol 1995;15:233-40.
  9. Duff K, McCaffrey RJ. Electrical injury and Lightning injury: a review of their mechanisms and neuropsychological, psychiatric, and Neurological sequelae. Neuropsychol Rev 2001;11:101-16.
  10. Silversides J. The neurological sequalae of electrical injury. CMAJ 1964;91:195-204.
  11. Pliskin NH, Fink J, Malina A, Moran S, Kelley KM, Capelli-Schellpfeffer M, et al. The neuropsychological effects of electrical injury: new insights. Ann NY Acad Sci 2004;888: 140-9.
  12. Kelley KM, Tkachenko TA, Pliskin NH, Fink J, Lee R. Life after electrical injury: risk factors for psychiatric sequalae. Ann NY Acad Sci 1999;888:356-63.
  13. Kopp J, Loos B, Spilker G, Horch R. Correlation between serum Creatinine kinase levels and extent of muscle damage in electrical burns. Burns 2004;30:680-3.