Clinical manifestations

Presentation and course

Most people struck by lightning survive: only about 10% of lightning strike cases are fatal, usually due to cardiac arrest. Among survivors, neurologic complications are the most devastating.

Neurologic complications of lightning strikes, varying from transient benign symptoms to permanent disability, have been categorized into four distinct groups (13; 67):

(1) Immediate and transient. These symptoms are often dramatic but are the most benign because they are fleeting. The symptoms include brief loss of consciousness, amnesia, confusion, headache, weakness, and paresthesias (77). Nearly 75% of patients have a brief loss of consciousness, and 80% have brief limb weakness and paresthesias, which usually normalize within a few hours (77).

Many patients experience a temporary lightning-induced paralysis called “keraunoparalysis” (78; 46; 50; 33; 67). The transient paralysis is accompanied by sensory loss, pallor, coolness of the limb, and extreme vasoconstriction (even to obliteration of the pulse in the limb) (78; 46). It affects lower limbs more than upper limbs and is specific to lightning victims.

Cerebellar dysfunction is an uncommon but established complication of lightning strikes (25; 06). Fortunately, the symptoms are usually temporary.

(2) Immediate and prolonged or permanent. The great majority of these complications involve the central nervous system. Often seen on imaging studies, these lesions can be devastating (71). Posthypoxic encephalopathy often ends tragically with death or serious cognitive deficits. As in other cases of out-of-hospital cardiac arrests, the prognosis for many of these lightning-strike patients is poor. Initial MRI and CT scan images often show evidence of cerebral edema. The relative contributions of lightning injury and secondary hypoxic-ischemic injury related to cardiac arrest are often unclear, but in some cases, well-executed Advanced Cardiac Life Support and Basic Life Support chain can result in return of spontaneous circulation and intact neurologic survival (01; 72).

Patients who have been struck by lightning can also present with an abrupt cerebral salt-wasting syndrome (37). Unless this problem is detected and treated, it can worsen cerebral edema.

Lightning-induced intracranial hemorrhages include subarachnoid and intracerebral hemorrhages (13; 10). The most susceptible locations in patients struck by lightning are the basal ganglia and the brainstem because electric current entering via cranial orifices (ie, eyes, ears, and nose) travels caudally toward the basal ganglia and brainstem (04). In contrast, cerebral infarction is an uncommon sequel of lightning injury, which is surprising because blood vessels and nervous tissues are selectively damaged with lightning (30). There is only one reported case of lightning-induced cerebral infarction evident on MRI (26).

Myelopathy is an uncommon but devastating complication of lightning strikes. Affected patients usually have permanent disability. However, occasional patients with spinal cord injuries do recover (51). The degree of functional independence through rehabilitation depends on a combination of factors, including injury severity, level, age, and motivation (52).

Other uncommon neurologic complications of lightning strikes include chronic epilepsy, locked-in syndrome, and radiculopathy (15; 01; 77).

(3) Delayed and progressive complications. Delayed sequelae are reported to follow lightning injuries by days to weeks and years, but whether the lightning was, in fact, the cause of the subsequent neurologic conditions is questionable in some cases. Delayed-onset cognitive deficits following lightning injuries have been attributed to posttraumatic stress disorder (68). Other delayed syndromes after lightning injury include motor neuron disease and movement disorders.

With delayed neurologic damage of vascular origin, free radicals resulting from oxidative stress may gradually damage vascular endothelial cells, cutting off blood supply or inducing late thrombosis and ending in neuronal death (69). With delayed demyelination without vascular damage, free radicals from oxidative stress may form directly from the abundant lipids in myelin cells (69). The “electroporation hypothesis,” the formation of additional pores in neurons, has been proposed to explain immediate or progressive changes in structure and function after lightning or electrical injury (69).

(4) Lightning-linked secondary trauma from falls or blast. Patients may sustain serious head or neck damage when they fall after a lightning strike or are propelled or thrown down by the lightning. Patients have developed subdural hematomas as secondary lesions. Many patients experience blast effects such as ruptured tympanic membranes.

By comparison with neurologic lesions seen after generated electrical trauma, peripheral nervous system lesions are uncommon following lightning. Autonomic nervous system disorders following lightning have rarely been reported (82; 28; 46). Cold temperature insensitivity is a symptom reported by some lightning survivors.

Many lightning survivors are beset with enduring neuropsychological and behavioral problems (87). Their symptoms can begin immediately or a few days or weeks after the lightning strike. These neuropsychological and cognitive deficits resemble those of traumatic brain injury, depression, and posttraumatic stress disorder (87). Similar neurobehavioral patterns are often seen in patients with electric injuries (44). Their symptoms often interfere with employment and family life. A questionnaire study of 100 lightning survivors revealed memory deficit, sleep disturbances, attention deficit, dizziness, chronic fatigue, irritability, depression, and fatigue (66). Other common aftereffects include pain syndromes (eg, backache, arthritis, and headaches). If these patients have not recovered by 3 months, they are at risk for long-term sequelae. The management plan for these troubling symptoms includes a team of empathetic physicians and reassuring counselors and association with understanding support groups.

There have been reports of patients developing encephalopathy after contact with ball lightning and corona discharges (34; 27; 13).

Ball lightning encephalopathy resembles the clinical condition seen in lightning strike patients. Ball lightning is an incompletely understood meteorologic phenomenon associated with lightning storms. Several centers have proposed models to explain the physics of ball lightning (02; 75). Ball lightning is mobile, luminous, vanishing, or exploding. These glowing spheres have been seen floating in the air, following telephone power lines, and traveling down the aisles of airplanes. Corona discharge, another induced electrical event associated with lightning storms, is a process by which a current flows from an electrode with a high potential into a neutral fluid, usually air, by ionizing that fluid to create a region of plasma around the electrode. Corona discharge remains near a conductor and does not move like ball lightning.

Very strong electromagnetic fields can be generated by lightning that can, in turn, generate induction currents in implanted electrodes and potentially even damage the brain (65). One reported case in which lightning affected implanted electrodes occurred in a 66-year-old woman who was being treated with a rechargeable deep brain stimulation system for neck dystonia; her implantable pulse generator switched off but remained undamaged when her apartment was struck by lightning (65). She suffered no neurologic consequences.

Prognosis and complications

Prognosis depends on many variables, including premorbid health and the time interval between the lightning strike and pre-emergency and emergency treatment.

The case fatality of lightning strikes is about 10% to 15% (23; 76). If a patient is conscious immediately or shortly after being struck by lightning, he or she is likely to remain alive.

Lightning current can reach a person via at least three routes: (1) direct strike, (2) side flash from a tall object such as a tree, and (3) ground current. Death and serious neurologic complications can result from all three routes. However, direct strikes to the head carry an especially poor prognosis with death or serious brain damage more than 50% of the time.

Initial physical symptoms generally resolved over time, with only about 10% to 20% continuing to experience physical symptoms more than a decade after injury (76). Among patients who experience neurologic symptoms, those with immediate and transient findings have the best prognosis. Those with immediate and prolonged or permanent neurologic manifestations have a more guarded prognosis for developing prolonged or permanent disability. Vision problems persist in approximately half of those injured by lightning (76). Some patients with cerebral infarction or cerebellar syndromes can improve and recover. By contrast, patients with posthypoxic encephalopathy often have a poor prognosis. Unfortunately, many die or are left with major cognitive problems. The prognosis is especially poor for those patients with prolonged coma and those whose myoclonic seizures are unresponsive to anticonvulsants. Patients with spinal cord injury often have permanent neurologic abnormalities.

Patients with neuropsychological and behavioral problems may have persistent symptoms; however, they may improve in time, especially with help from concerned physicians and an understanding support group. Psychological symptoms, such as depression or anxiety, often have a later onset and are more likely to be chronic (76).

Clinical vignette

A 29-year-old man was hit by a lightning strike while farming (01). Cardiopulmonary resuscitation was provided first by coworkers and later continued with success by the medical rescue service. After advanced cardiac life support with therapeutic hypothermia, he was recognized to have quadriplegia with facial diplegia. MRI was consistent with hypoxic-ischemic encephalopathy, and diffusion-weighted MRI showed marked damage along the corticospinal tract. A reactive electroencephalogram pattern and, ultimately, his ability to communicate with eye blinking supported the clinical diagnosis of locked-in syndrome. Two weeks after admission, he was transferred to a neurologic rehabilitation center. In this case, direct lightning-induced damage, secondary hypoxia from his cardiac arrest, or both may have contributed to his neurologic impairment.

Biological basis

Etiology and pathogenesis

Lightning damages tissues and organs through mechanisms that include thermal effects, electrical current effects, induced electrical currents, blast effects, injuries related to falls, and electroporation. Histopathologically, fatal cases may show fresh bleeding in the subarachnoid and subpleural spaces and interlobular rupture in the lungs (60).

Because lightning is associated with temperatures of 30,000 K, it is unsurprising that thermal burns often accompany lightning. Skin burns may occur when water or perspiration boils under heated metallic jewelry.

Lightning generates a large magnetic field. An individual in the vicinity of a lightning strike can experience enough magnetically induced current to produce destructive effects (09). When current enters the body, it flows through (and can damage) tissues with the least resistance (54). Tissues with high fluid and electrolyte content are blood vessels and nerves. In addition to the damaging effects of direct lightning current, magnetic field changes associated with lightning may induce a loop current with the body (22). These induced currents may be responsible for asystole or ventricular fibrillation. Low-intensity lightning can cause ventricular fibrillation without leaving skin marks (81).

Electroporation refers to nerve cell membrane defects produced by electric currents too weak to cause heat injury yet strong enough to damage the lipid layer membranes (53).

Epidemiology

In the United States, most lightning casualties occur in the Southeastern and Rocky Mountain states (55). Florida’s central Gulf Coast has more lightning strikes and thunderstorms than any other place in North America (32). From a global analysis, the highest number of lightning storms occur in the mountains of Rwanda.

Many available data on lightning casualties and fatalities are found in Storm Data, a monthly National Oceanic and Atmospheric Administration (NOAA) publication. Because the source of the data was compiled primarily from newspaper clippings, those numbers were underreported (56). For the years of 1959 to 1994, Storm Data reported 9818 injuries and 3239 deaths, or a ratio of approximately three to one (31). However, these Storm Data results underreported the number of lightning injuries by at least 50% and fatalities by 10%, a bias in favor of fatal outcomes, likely because fatal strikes are more likely to receive media attention (05). The National Center for Health Statistics reported 1906 lightning fatalities in the United States between the years of 1979 and 2004 (79), with the largest number of lightning deaths in Florida and Texas (03). A Colorado study, based in part on hospital information using codes of lightning injury in both inpatients and outpatients, reported a 10-to-1 ratio of casualties to fatalities (23).

In the earlier part of the 20th century, lightning victims were more likely to be men working farming and ranching, as continues to be the case in less developed countries (60). In the United States and other highly developed countries, lightning victims are more likely to be engaged in outdoor recreation and sports in the latter part of the 20th and early 21st century (55). These activities include golf, mountain biking, hiking, camping, swimming, boating, fishing, horseback riding, and ball-field sports (12). The risks are much higher during summer months, but even winter sports, such as skiing, pose some risk (17).

The typical lightning strike victim is a healthy male in his mid-30s. Males outnumber females by about 4.5:1. This ratio is consistent with data from Colorado and Sweden (38; 12).

Lightning strike during pregnancy is rarely reported in the medical literature or the news media, but when it occurs, it may be associated with fetal ischemic brain injury (40).

Prevention

Lightning injuries are especially tragic because the victims are often healthy, young people engaged in sports or recreation when suddenly and seriously injured. Individuals at risk should understand what measures must be taken to reduce the risks of being struck by lightning. It is imperative that adults in charge of children, such as teachers, coaches, counselors, and lifeguards, know and implement lightning safety guidelines (73).

Individuals should have a lightning safety action plan before initiating an outdoor sports or recreation activity. That plan should include knowledge about the weather patterns of the location where he or she is located. For example, Rocky Mountain climbers should know that the high-density lightning-flash hours increase after late morning and continue during the afternoon and evening. Therefore, mountain climbers should plan the climb so that they begin early in the morning and are off the mountain by 11:00 AM (12).

Unfortunately, lightning tragedies occur even when the skies are clear. Patients have been struck by “bolts from the blue” (18; 47).

Lightning safety recommendations were drafted in 1998 by the Lightning Safety Group and should be understood by all those at risk of lightning strike (88). If an individual can see lightning or hear thunder, he or she is already at risk. Outdated "flash-to-bang" thresholds to seek shelter should not be used (73). Although no place is absolutely safe, there are places of low risk. To reduce the risk of being struck by lightning, one should seek shelter in a large structure (eg, school, office building, house) that has plumbing and electrical wiring. A fully enclosed metal vehicle is a relatively safe place. By contrast, standing or leaning on the outside of a car or bus is a dangerous situation. Other places of high risk to avoid include isolated trees, flag poles, open fields (including ball fields and golf courses), swimming pools (indoor and outdoor pools), beaches, rivers, and metal fences. Golf carts, bicycles, and motorcycles are unsafe during lightning storms (See Table 1).

Table 1. What to Avoid During Lightning Storms

Golfers should avoid standing under an isolated tree. Too often golfers make the mistake of seeking shelter from the rain under a single tree and place themselves at risk. Golf carts are not safe. The golfer should stay inside the clubhouse.

Bicyclists are vulnerable to lightning strikes in the open. Rubber tires do not protect from lightning. The bicyclist should find a safe building or enclosed motor vehicle.

Lightning danger may persist for up to 30 minutes after the last evidence of thunder or lightning. Therefore, remaining in a safe shelter for 30 minutes before returning to the outdoor activity is prudent.

Much of the sound advice on lightning safety known in the 21st century was available over 60 years ago:

Differential diagnosis

Because most lightning strike cases are witnessed by the victim or others nearby, there is usually little or no question about the cause of the patient’s neurologic complications. However, when lightning is the cause of death and there are no witnesses, the cause of death may not be obvious. When investigating sudden unexpected death of individuals discovered outdoors, the common differential diagnoses include cardiac arrhythmia, cerebral hemorrhage, seizures, pulmonary embolism, trauma (falls, suicide, homicide, animal attacks, etc.), and lightning (12).

Forensic clues suggesting lightning strike include ruptured tympanic membranes, skin lesions of burns and ferning patterns (Lichtenberg figures), and burned clothing and shoes (41; 07; 80). Lichtenberg figures are pathognomonic of lightning injury (20; 41; 07; 80).

Other tools now available to the investigator are satellite and meteorologic data from the National Lightning Data Network. Such data can prove that lightning did occur where the victim was found and can identify the time of the lightning.

Diagnostic workup

Most permanent neurologic complications of lightning injury involve the central nervous system (brain and spinal cord) rather than the peripheral nervous system.

Imaging studies are important in determining the site and nature of the lesion in the brain and spinal cord. For example, a CT scan of the head helps identify intracranial hemorrhages (61) and may show massive loss of grey-white matter differentiation, especially involving the fronto-temporal lobes bilaterally (71). Cranial MRI helps evaluate neurologic complications, such as posthypoxic encephalopathy, cerebral infarction, and cerebellar atrophy (25). Unilateral hemispheric leukoencephalopathy on MRI has been reported as an incidental finding in an individual who sustained a lightning strike during infancy (49).

Standardized autonomic nervous system testing procedures might corroborate the diagnosis for those few patients with autonomic nervous system involvement symptoms.

Ophthalmology consultation should be considered to evaluate possible eye injury, including delayed cataracts. Otologists may be needed to treat a ruptured tympanic membrane, a common complication of lightning strikes.

For patients with neuropsychological symptoms, neuropsychological assessments and psychometrics may be helpful (36).

Management

One should begin emergency evaluation and treatment on finding the patient immediately or shortly after lightning has struck. If the patient is unconscious, one should begin basic life support, including airway, breathing, and circulation assessment. Cardiorespiratory resuscitation should be instituted immediately if the patient is apneic and has no pulse (29; 88). These patients may have cardiorespiratory arrest with ventricular fibrillation.

The lightning-strike patient does not hold an electrical charge. For that reason, the rescuer need not fear receiving a shock from touching a lightning-strike patient. This is not always the case with patients who are shocked by electrical lines or appliances; in those situations, the rescuers should ensure electrical current’s source is off or safely removed from the patient. In a lightning situation, rescuers should be careful not to place themselves in danger of being injured by another lightning strike. If rescuers have a mobile phone, they should call 911 for help. The chances of survival are good for the patient struck by lightning who is conscious. However, persistent medical complications are possible.

More neurologic issues are evaluated in an emergency department, outpatient facility, or hospital. Many neurologic complications (such as keraunoparalysis, brief loss of consciousness, confusion, and paresthesias) are immediate and transient; these symptoms should be carefully evaluated but often require no specific treatment. Unfortunately, other patients have permanent or prolonged neurologic sequelae that call for the expertise of many disciplines, including neurologists, cardiologists, neurorehabilitation specialists, intensivists, and others.

The prolonged and permanent neurologic complications of lightning strikes involve damage to the central nervous system, including cerebral disorders, spinal cord injury, and neuropsychological symptoms (85). Patients with catastrophic brain damage will require elaborate measures provided by intensive care units. A comprehensive rehabilitation plan can be instituted in time and with improving mental status (including physical, speech, and occupational therapies). A protracted comatose state and myoclonic seizures unresponsive to anticonvulsants are indicators of poor outcomes.

Early neurorehabilitation is essential for patients with spinal cord injuries (85). Patients with a spinal cord injury may confront many problems, including neurogenic bladder, skin sores, deep vein thrombosis, and severe spasticity. The management plan for lightning-related spinal cord injury is the same as that for other patients with traumatic spinal cord injury.

Neurosurgical consultation should be obtained for patients who suffer intracranial hematomas and spinal cord injuries resulting from falls and blasts associated with lightning. These lightning-linked lesions to the head and spine can be catastrophic. Intracranial hemorrhages (including epidural, subdural, and intracerebral hemorrhages) can be rapidly fatal. CT scan of the head should be obtained on an urgent basis.

Many lightning survivors are plagued with persistent neuropsychological and behavioral problems. Their symptoms (including impaired concentration, sleep disturbances, depression, chronic pain, and easy fatigability) can begin immediately or after a few days and may persist for months or longer. The problems can interfere with employment and family life. Patients may improve with time, especially with assistance from concerned physicians, psychological counseling, and an understanding support group.

Special considerations

Pregnancy

A literature review of lightning strikes in pregnancy reveals less than 20 reported cases. Although maternal prognosis for survival was good, the literature revealed a dismal outcome for the fetus (11; 42; 63). Fetal or neonatal death was reported in nearly 50% of the cases. Explanations for these catastrophes include (1) severe uterine contractions and uterine rupture and (2) the uterus and amniotic fluid are good conductors of electricity (83; 39). A fetal autopsy after a lightning-induced miscarriage revealed interstitial hemorrhages of the lungs (11).