Clinical manifestations

Presentation and course

Categories of neurologic sequelae that may result from electrical injuries include the following:

In nonfatal injuries, the clinical course can be variable. Opinions differ about the nature and cause of patient symptoms and the relationship between symptoms and factors like trauma severity, litigation, or premorbid personality. Not all survivors develop physical, cognitive, or emotional difficulties. No consistent relationship has been established between characteristics such as age, injury-related characteristics (eg, voltage, current source, work error), and neuropsychological test performance. Low-voltage electrical injuries usually produce more frequent long-term sequelae than high-voltage injuries.

Neurologic sequelae. Neurologic sequelae of electrical injury are diverse and can include loss of consciousness, confusion or encephalopathy, memory disturbance, seizures, cerebrovascular complications (eg, cerebral hemorrhage, cerebral ischemia, and cerebral venous thrombosis), cerebral edema, hydrocephalus (01), movement disorders (eg, tremors, dystonia, myoclonus, parkinsonism, choreoathetosis, and myokymia), speech impediment or mutism (22; 46), headache, neuro-otological problems (eg, sensorineural hearing loss, tinnitus, dizziness, and vertigo) (48; 80), facial palsy and other cranial nerve dysfunction (60), meningitis, myelopathy, autonomic nervous system complications (eg, reflex sympathetic dystrophy or complex regional pain syndrome), peripheral neuropathies (79), and various muscular symptoms (eg, muscle aches, spasm, cramps, and twitches).

Some uncommon neurologic electrical injuries include the following:

In a study on patients with mild cognitive impairment following electrical injury, cerebral blood volume maps showed hypermetabolism in the cerebello-limbic system, but diffuse tensor imaging did not identify any microstructural changes (51).

Neuro-urological electrical injuries. Neuro-urological electrical injuries may occur secondary to brain or spinal cord trauma or as independent consequences of electrical shock (81). The main urological functions that can be affected by an electrical injury are lower urinary tract function, erectile function, and renal function:

Neuropsychological symptoms. These may include memory disturbance, increased emotional sensitivity, insomnia, unusual anxiety, reduced attention span/loss of concentration, personality changes, fear of electricity, and inability to cope. Some neuropsychological symptoms are compatible with posttraumatic stress disorder, which had an estimated prevalence of 7.6% in a retrospective study of 311 cases of occupational electrical injuries (57). Posttraumatic stress disorder is characterized by intrusive thoughts, nightmares and flashbacks of past traumatic events, avoidance of reminders of trauma, hypervigilance, and sleep disturbance, all of which lead to considerable social, occupational, and interpersonal dysfunction. A diagnosis of posttraumatic stress disorder is made for patients older than 6 years of age who meet all the DSM-5 criteria for the syndrome (05).

Nonelectrical effects. With higher power density and smaller, more compact spaces, there is an increased risk of damage from explosive effects with characteristics of closed blast injury.

Blast can result in tissue destruction from shrapnel, confined space air contamination, acoustic or pressure effects, and acceleration-deceleration forces. Traumatic brain injury can occur despite an intact skull. When a patient’s neurologic presentation is consistent with blunt force or blast injury after an electrical event, consideration should be given to the possibility of exposure to an electrical explosion scenario complicating an electrical shock.

Prognosis and complications

Survival from electrical injury can be associated with significant functional impairment. In a landmark retrospective study of employees of a national electrical energy company, the electrical trauma survival experience from 1970 to 1989 was reviewed for a workforce between 100,000 to 120,000 persons (29). Electrical injuries affected 2080 workers. Of these, 515 patients, or 25%, had postinjury complications, including burn-related complications (63%), neuropsychiatric complications (18%), sensory impairment (12%), amputations (5%), orthopedic injury (5%), and cardiovascular impairment (1%).

Sense organ disorders included anosmia; vision-related changes due to conjunctivitis, keratitis, and cataracts; and neuro-otological sequelae with conductive or sensorineural hearing loss, tinnitus, and vertigo. In 59 of the 515 patients, disability was considered serious, with an impairment rating from 31% to 100% (29).

Neurologic complications of electrical injury. Acute CNS complications are well-recognized and cause an increased risk of morbidity, whereas peripheral nervous system complications are less predictable after electrical injuries.

Delayed neurologic sequelae include hydrocephalus, cerebral venous thrombosis, and amyotrophic lateral sclerosis and usually carry a great risk for permanent disability (81). However, a case of acute-onset quadriplegia following a high-voltage electrical injury, with no radiographic abnormalities, regained partial sensorimotor function 2 months after the injury (21).

Cases of delayed-onset of visual symptoms have been reported in whom MRI showed bilaterally symmetrical diffusion restriction in the parietal and occipital cortex, and improvement followed intravenous steroids (17; 49).

Osteoporosis may develop as a complication of electrical skin burns and is explained by prolonged sympathetic nervous system dysfunction, which may result in bone metabolism derangement even after the acute phase of electrical burn (62). Other contributing factors include prolonged bed rest and immobilization, as often occurs with severe burns or other injuries.

Measures of physical morbidity, as measured by total body surface burned, total days in intensive care, and hospital length of stay, have been traditionally used as predictors of outcome in high voltage electrical injuries, but functional outcomes, including neuropsychological sequelae, are similar between disparate levels of electrical injury as judged by voltage (18). Electrical injuries may incur severe morbidity despite relatively small burn size or low voltage (18).

Biological basis

Etiology and pathogenesis

Etiology. Table 1 highlights nonoccupational causes of electrical injury.

Table 1. Causes of Nonoccupational Electrical Injuries and Fatalities

Conducted electrical weapons (CEWs). Stun guns and Tasers have been developed for use by law enforcement and security personnel to provide less lethal alternatives to conventional weapons. These devices deliver bursts of high-voltage, low-amperage direct current, either through a handheld device (stun gun) or through a hook-and-wire system fired using compressed gas (Taser). CEWs are widely available and have been used for criminal purposes and torture. The authors of two systematic reviews concluded that prolonged observation and diagnostic testing are not necessary in patients who are otherwise asymptomatic and alert following such an exposure (53; 75). However, in rare instances, various adverse outcomes related to the use of electrical weapons have been described. Examples include cardiac arrhythmias resulting from fatal, blunt, or penetrating injuries, and neurologic sequelae such as seizures, altered mental status, and ischemic stroke (09). With 16 case reports in the literature, the use of Taser presents a small but real risk of death from fatal traumatic brain injury due to a fall, and old age represents an independent risk factor for such fatalities (38).

Electroconvulsive therapy (ECT). ECT is still used for the treatment of some psychiatric disorders and typically causes some amnesia (16) or headaches (63) and rarely may produce other neurologic disturbances. Usually, the peri-event amnesia and neurologic complications of ECT are transient, but this is not universally true. Headaches are usually mild and short-lasting, but recurrent common migraine has been reported (63).

As argued by proponents of dlectroconvulsive therapy (23):

Pathogenesis. Electrical injuries can include tissue damage from the flow of current through the body, arc flash, or clothing that catches fire.

Table 2. Effects of Electrical Current on the Body for Source Currents of Less than 600 Volts

Burn hazard is present from ohmic heating (also called joule heating) due to the flow of electrical current through a conductor (including the body); ignition and combustion of nearby materials, notably worn clothing and adjacent equipment; and sprayed or blown hot or melting installation elements moved by mechanical forces if an electric arc accompanies the electric shock exposure.

Skin burns result from high-temperature exposures at the body surface. High-temperature exposures that occur volumetrically or distribute within the body’s tissues are also called burns. The outward appearance of an electrical burn does not accurately predict the true extent of the injury because internal tissues and organs may be much more severely burned than the skin. Neurologic tissue damage from electrical deep tissue burns usually manifests during triage assessment.

Electroporation, a process by which an electrical field induces the formation of pores through the cell membrane allowing free passage of ions and fluid, has been identified as a primary cause of neurologic injury following electrical exposure (13). Other mechanisms of injury may also play a role, such as the breakdown of the cytoskeleton due to excessive intracellular calcium.

Electrocution typically results when passage of an electrical current through the body disrupts cardiac, respiratory, or neurologic function, for example producing ventricular fibrillation or respiratory arrest by damage to brainstem respiratory centers (15). Most electrocution deaths are accidental, with suicides being less common and homicides being very rare (15).

From a clinician’s viewpoint, knowledge of the electrical event’s voltage conditions alone is of limited helpfulness because the extent of survivor’s electrical injury is a function of the power frequency energy transfer due to a combination of the current density in the tissue and the contact duration. Similarly, from a medical perspective, the heat, radiation, and pressure damage to the body are predicated on the efficiency of the electromechanical and electrochemical coupling between the hazardous source, event space, and the body. This information is not usually available to the medical team.

Regardless of the means of transmission, electricity enters a victim at an “entrance” point, travels a certain path, and leaves via an “exit” point. Entrance points can come in direct or indirect contact with the source of electricity and may or may not suffer burns when the electrical current meets the skin’s resistance. The most common entrance points are the hands and the head. Exit points allow the electricity an avenue to proceed to a grounding source. Although the path of the electrical current determines the exit point, some of the most common exit points are feet, legs, and hands. The exit of the current from the body may be a violent event leading to extensive damage. In cases of AC contact, the terms entrance and exit points may be moot because the electrical current is continuously flowing into and out of the individual through the same point.

The path of the electrical current through the body is determined by the path of least resistance as the current proceeds to a grounding source (ie, the earth). Different tissues in the body have different resistance levels, and electrical current preferentially follows those tissues with the least resistance. Because nerves and blood vessels have low levels of resistance compared to bones and fat, the current tends to travel along nerves and blood vessels when it overcomes the resistance of the skin. This may be 1 reason for the high rates of neurologic, psychiatric, and neuropsychological sequelae associated with electrical injuries. However, if the current is dense enough, it will flow through whatever is in its path en route to the ground (eg, muscle, tendons, bones). Common pathways through the body are hand-to-hand, hand-to-foot, or head-to-foot.

Hand-to-hand pathways are associated with a greater mortality risk, presumably because vital organs (eg, the heart) are in that path. It is reasonable to assume that pathways from the head-to-anywhere would be associated with higher levels of neuropsychological impairments because the brain falls in the path. However, severe cerebral disruption may result from electrical injuries, even when the brain is not directly in the primary path of maximal current flow through the body. For example, bilateral diffuse leukoencephalopathy occurred in an electrocuted woman even though the electric current entered one hand and exited through her legs without affecting the head directly (34).

Alternating current (AC) is several times more dangerous to the body than direct current (DC); there are two primary reasons for this. First, AC can cause tetanic spasms in muscles leading to repetitive contractions of those muscles. For example, if an individual’s hand contacts AC via an exposed electrical wire, the hand muscles in the hand may contract, and the individual will be unable to let go of the wire (ie, “no let-go” response), leading to an increased duration of electrical contact. Second, the cardiac and respiratory systems appear to be especially sensitive to AC, and damage to those systems can lead to severe sequelae or death.

After a severe electrical contact injury, a survivor’s injured muscles can swell massively due to cell membrane damage, leading to a rise in local extracellular pressures identified clinically in tissues as “compartment syndrome.” In compartment syndrome, the blood supply to the affected muscle is compromised, and oxygen supply is diminished. With hypoxia, further metabolic compromise and tissue destruction may result, leading to neuronal injury, further vascular compromise, and possible gangrene.

Other significant features of severe electrical exposure include disturbances in cardiac conduction, with possible refractory or life-threatening cardiac arrhythmias.

Direct damage to the nervous system and delayed indirect effects, such as denervation hypersensitivity, ephaptic transmission, oxidative reactions, and aberrant neuronal sprouting, are hypotheses proffered to account for electrically induced neurologic sequelae.

Morphological changes in the CNS are diverse following electrical injury and include neuronal chromatolysis, neuronophagia, and neuron loss. Infiltration of macrophages and neutrophils via the blood-brain barrier is seen, and microglial activation is a prominent and early event in CNS damage (33). Cellular DNA damage and excitotoxicity mechanisms may also contribute to ongoing and progressive damage following electrical trauma.

Delayed neurologic injury following electrical injury is poorly understood (61). If the delayed neurologic damage has a vascular origin, free radicals resulting from oxidative stress may gradually damage spinal vascular endothelial cells, cutting off blood supply and ending in the death of spinal neurons. When the delayed condition is demyelination without vascular damage, the free radicals from oxidative stress may be formed directly from the abundant lipids in myelin cells. The electroporation hypothesis, the formation of additional pores in neurons, may best explain immediate or progressive changes in structure and function after electrical injury.

Epidemiology

Approximately 1000 deaths per year occur in the United States from electrical injuries. Of these, approximately 400 are due to high-voltage electrical injuries.

Electrical power-line installers and repairers are among the 10 civilian occupations with high fatal-work-injury rates. Their rates of fatal work injuries per 100,000 full-time equivalent workers were 20% in 2011, 24% in 2012, 22% in 2013, 19% in 2014, and 21% in 2015. Telecommunications line installers and repairers had published rates of 8% in 2013 and 10% in 2014. In comparison, the rates for all workers from 2011 to 2015 ranged from 3.3% to 3.5%. During the same period, the rates of nonfatal occupational injuries (per 10,000 full-time equivalent workers) for electrical power-line installers and repairers were considerably higher than for all occupations. In addition, the nonfatal rates for telecommunications line installers and repairers were higher than those for all occupations and for electrical power-line installers and repairers.

Predisposing factors for fatal outcome of electrical injuries at the workplace include the following:

In an epidemiological study, risk of electric injury was assessed using occupational accident registries across Europe (32). Of 116 job codes, occupations with high potential for electric injury exposure were electrical and electronic equipment mechanics and fitters, building frame workers and finishers, machinery mechanics and fitters, metal molders and welders, assemblers, mining and construction laborers, metal-products machine operators, ships’ decks crews, and power production and related plant operators.

A retrospective cohort study on the risk of neurologic diseases among 3133 people in Denmark who had survived an electric accident from 1968 to 2008 suggested an association between a single electric shock and increased risks for peripheral nerve diseases, migraines, vertigo, and epilepsy (30).

Prevention

Most electrical injuries are preventable, and public service announcements have attempted to disseminate needed safety precautions beginning with the increasing availability of electrical power in homes in the 1920s.

The goal of avoiding electrical injuries has guided the development of safer consumer product and industrial equipment designs (eg, grounded plugs, ground fault circuit interrupter [GFCI] outlets in bathrooms, specified space clearances, venting systems on equipment to discharge combustion products, “umbilical corded” controls, infrared monitoring ports for doors-closed heat monitoring) and barrier protection (such as leather gloves, flash suits, safety glasses, face shields, long sticks, extended handles, and flame-resistant clothing).

By reducing the amount of possible energy transfer during an unintentional electrical exposure, strategies including equipment design and barrier protection can increase the likelihood of survival after an electrical incident.

These strategies include:

These strategies do not necessarily effectively eliminate the heat hazard from an unintentional electric arc. Consequently, additional protection strategies to reduce occupational exposure are needed. Results of a retrospective study of electrical burn patients admitted to the burn centers in South China indicates that more attention should be paid to preventing electrical burns in male adults, with a particular focus on industrial workers, incidents in the spring and summer, and high-voltage injuries (25).

Differential diagnosis

Confusing conditions

Neurologic complications of electrical injuries should be differentiated from those due to lightning, particularly in a patient who is not conscious and when history or injury circumstances are not available.

Differentiation from other neurologic conditions resembling complications of electrical injury. The differential diagnosis of the neurologic complications of electrical injuries may include those related to anoxia/hypoxia, cardiac arrest, convulsions, explosion/blast effects, falls, or mechanical trauma from the affected individual being caught by machinery or moving equipment.

Detection of malingering. The rate of malingering is as high as 40% in compensation-seeking workers in general and 25% in electrical injury in particular (47). Many electrical injury patients report neurocognitive impairment or movement disorders. Although entry and exit wounds indicate that the body has absorbed sufficient electricity to cause injury, their presence does not necessarily indicate that the electrical exposure has caused nervous system injury. At the same time, the absence of entry and exit wounds does not necessarily mean that electrical injury has not occurred. Therefore, other indicators of acute CNS dysfunction, such as those used to grade transient brain injury severity (eg, Glasgow Coma Scale score, length of coma or posttraumatic amnesia, structural damage to the nervous system), may also be helpful. Criteria have been developed to provide a systematic, comprehensive, integrated, research-based approach to diagnosing malingered neurocognitive dysfunction (69), and these have been applied to individuals reporting electrical injury (10). Among 11 patients evaluated for neurocognitive impairment after electrical injury, over half of them met the criteria for at least probable malingered neurocognitive dysfunction, and most of the patients with malingered neurocognitive dysfunction lacked evidence of a biologically meaningful exposure to electrical current (10).

Diagnostic workup

In general, the diagnostic approach to the neurologic consequences of an electrical injury patient is consistent with the neurologic evaluation of a multi-trauma injury patient. A high degree of clinical suspicion for neurologic involvement is warranted, especially when no or limited information about the responsible electrical events is available and no external wounds indicate localization of exposure.

Table 3. Investigation of Electrical Injury to CNS, Muscle, and Peripheral Nerve

Management

American Burn Association Advanced Burn Life Support guidelines outline triage, initial resuscitation, and emergency transport protocols in the emergency or first-response period. Cardiopulmonary resuscitation at the scene can be lifesaving, as was powerfully shown in the "Kiss of Life" Pulitzer Prize-winning photograph by Rocco Morabito in 1967 (70).

On admission to emergency medical services, physical examination, laboratory studies, and diagnostic radiology evaluation are prioritized, depending on the patient’s clinical course. Cardiac monitoring should be initiated in all patients that have experienced anything greater than a minor low-voltage burn.

Neurologic evaluation of the CNS and auditory, visual, and peripheral sensorimotor function can be managed simultaneously by stabilizing cardiorespiratory status and wounds.

Electrical injuries are traditionally divided into low-voltage electric power injuries (less than 1000 V) and high-voltage (greater than 1000 V). In contrast to other types of trauma, high-voltage injuries require a high index of suspicion and awareness of possible manifestations. Electrical injury should be viewed and managed as a multisystem injury (20). Hospital admission is warranted when there is evidence or suspicion of electromechanical contact with an electrical source of more than 200 V potential and capable of more than 200 mA, even without physical findings.

Additional indications for hospital admission include the following occurrences after electrical injury: history of cardiopulmonary resuscitation or cardiac findings, including refractory cardiac arrhythmias; history of loss of consciousness or disorientation; history of fall from a height; associated thermal injury to greater than 15% of the body surface area, or including burn to the hands, feet, face, or groin; suspicion of smoke or vapor inhalation or respiratory distress; spine fractures; serum electrolyte derangements; and compartment syndromes.

Burn care teams must also address the impending neuropsychiatric sequelae of patients with electrical injuries as a routine part of multidisciplinary care. Although the rehabilitation and resuscitation phases of burn care may partly determine neuropsychiatric outcomes, these outcomes may, in turn, determine reconstructive success. For example, posttraumatic stress disorder increases anxiety before, during, and after painful medical procedures. Patients with electrical injuries may benefit from earlier, more focused, and intensive psychiatric support. Although useful guidelines and models exist to systematically address the complex physical morbidities of patients with electrical burns, newer models and strategies are needed to prevent and treat neuropsychiatric sequelae (18).

Special considerations

Pregnancy

Limited information is available regarding pregnancy and delivery following electrical shock exposure. Effects of electrical injuries during pregnancy range from a transient unpleasant sensation with no effect on the fetus to sudden maternal and fetal death. Reported adverse effects include fetal heart abnormalities, damage to the fetal CNS, and fetal growth retardation (72).

Anesthesia

Considerations regarding anesthesia are related to trauma severity and level of neurologic impairment.