Strangulation Injuries

Etiology

Strangulation is defined as the compression of blood or air-filled structures which impedes circulation or function. In this summary, strangulation will refer to compression of anatomical neck structures leading to asphyxia and neuronal death. Strangulation injuries can be divided into several categories. These include hanging injuries, manual strangulation, and ligature injuries.[9][10][11][12]

Hanging injuries can be further divided into specific categories. Complete hanging is defined by the full weight of the patient being suspended by the neck. Incomplete hanging injuries encompass all injuries in which the patient is supported partially by another object such as the ground or furniture. For centuries hanging has been used in the penal systems as a form of punishment. The term “well-hung” referred to the erection a male experienced after a proper hanging was performed. This method of execution usually involved dropping the person from a height equal to or greater than their height, which often resulted in spinal fractures, spinal trauma, and spinal shock causing priapism.[13] Classically, hanging injuries have also been associated with vascular pathology ranging from carotid intimal tears to complete rupture.[14]

Ligature and manual strangulation injuries occur when a force that is independent of the patient’s body is applied to the neck. Strangulation injuries can also be divided into categories of intent. These include homicidal, suicidal, accidental, and auto-erotic.[2][15] The material involved in a ligature or hanging may also have implications on pathology and subsequent forensics.[16]

A significant number of pediatric strangulation injuries are accidental.[6] The unique behavioral characteristics of different ages highlight the mechanisms among these injuries and deaths. Younger children may suffer from injuries related to car windows, electrical cords, and becoming trapped between furniture (including high-chairs designed for children).[17][18] Accidental or intentional suffocation injuries, a mechanism distinct from strangulation via which asphyxia occurs due to oral-nasal obstruction, may also be part of the presenting situation.[16] Playground and handle-bar strangulation injuries, while rare, are important etiologic factors to consider in polytrauma pediatric patients with supporting histories.[19] As mentioned earlier, social media influences play a critical and more contemporary role in teenage and adolescent populations. The literature describes auto-erotic asphyxiation as a more common mechanism in this population as well and constitutes a mechanism of injury that can be considered both intentional and accidental. 

Strangulation injuries can occur during partnered sexual activity – either intentionally, accidentally, or both. It is a dangerous form of intimate partner violence, and survivors are at high risk for becoming victims of homicide.[20] Conversely, consenting adults engaging in low-force activity to enhance pleasure may sustain devastating injuries if care is not taken. Additionally, auto-erotic asphyxiation is seen in the adult population of strangulation injuries and is described as a paraphilia.[21]   

Many “submission holds” within the world of martial arts are known to place direct pressure on cervical structures and can result in strangulation injuries. Along similar lines, police and military combatants are given training on "vascular neck restraint." This effective, but controversial, approach to subduing a target can result in permanent and debilitating injuries or even death.[22]

Epidemiology

The true prevalence and incidence of all-cause strangulation injuries and mortality is unknown. Because of the diversity of etiologies that lead to the common injury pathway, epidemiological studies, and case series within the literature tend to be etiology and population specific. 

Hanging injuries are the second most common cause of suicide in the United States; whereas, gunshot wounds are the leading cause. Males are more likely to commit suicide in both of these manners.[23] Women in abusive relationships are at the greatest risk of strangulation injury. Epidemiological studies and medical literature may underrepresent the true incidence and prevalence due to patient underreporting when medical attention is sought.[2] The incidence of hanging injuries has been increasing in the United States over the past several years, though as a cause of death in homicide cases it has remained fairly unchanged from 2006-2013.[3] The popularity of “choking games” amongst pre-teens and teens has also affected the escalation of these injuries.[24]

In a retrospective case series published by Berke et al (2019), 98 near-hanging patients were identified over an 11-year period. All patients underwent trauma evaluation, and 254 CT and MRI scans were performed, which discovered only 8 traumatic injuries. Two patients demonstrated injuries to the cervical vasculature, three patients showed signs of thyroid cartilage and hyoid bone fractures, and three patients had vertebral injuries. A total of 35.7% of patients had clinically diagnosed anoxic brain injury, which was deemed present in all 19 patients who expired (19.5%). Injuries were more common in patients with a low Glasgow Coma Scale (GCS) compared with those exhibiting a normal GCS.[25] 

Pediatric patients less than 1 year of age unintentional strangulation injuries ranks fourth among all causes of unintentional injury. Motor vehicle accidents, drownings, and burns are all more common. Of over 200,000 playground injuries recorded in 1999, only 0.07% were fatal, and of these 50% were determined to be caused by asphyxia from strangulation injuries. Eighty percent of victims were found to be under 10 years of age.[6]

Pathophysiology

The common pathway through which strangulation injuries cause morbidity and mortality is via cerebral hypoxemia and resultant cerebral ischemia. Four specific pathways are described in the literature.[26]

1. External pressure to the jugular veins prevents adequate venous return from the cerebral circulation. Backpressure prevents eventual arterial inflow and results in elevated intracranial pressures. This ultimately results in unconsciousness, depressed brainstem functions, and ultimately asphyxia and death.
2. External pressure to the carotid arteries directly prevents oxygenated blood flow to the cerebral vasculature which leads to asphyxia and death.
3. Pressure obstruction of the larynx primarily results in the inability to oxygenate the pulmonary vasculature. Systemic hypoxia quickly ensues of which the most pronounced effects are rapid loss of consciousness followed by death.
4. Though rare, cardiac dysrhythmias may occur with pressure directed towards the carotid bodies bilaterally. This has the potential to evoke cardiac arrest, and subsequent death if not promptly recognized

Acute sequelae of rapid (or slow) loss of perfusion include various forms of anoxic brain injury. Watershed infarcts can occur in patients with chronic cerebrovascular disease. Ultimately, with a significant initial injury, diffuse cerebral edema can result which may lead to various forms of brain herniation and death. Diffuse axonal injury has also been described in the autopsy literature.

Pathophysiologic phenomenon can also be grouped in relation to the aforementioned three categories of strangulation - hanging, manual strangulation, and ligature-based injuries.

The nature of the hanging injury informs the type of pathophysiology. Judicial hangings from height can result in rapid deceleration mechanisms. Mechanical forces transmitted in this manner can result in what is described as “internal decapitation” – spinal cord transection, cervical vascular transection, and various types of spinal fractures. Classically, the "hangman's" fracture is described when deceleration causes forceful extension of the neck resulting in bilateral C2 pedicle fractures. If the force is severe enough C2 can become severely subluxated from C3, thus threatening the spinal cord. Associated hematomas may also result in neurological compromise. These fractures have been described in motor vehicle accidents where the top of the steering wheel immediately halts the forward movement of a patient's neck (should an airbag not be present) resulting in a similar hyperextension injury. Manual strangulation or hanging without a significant height drop implies less deceleration force, and fractures are not typically common in this population. Many types of cervical spine injuries in these patients are described as unstable.[26][27]

Compression of the jugular veins results in acute death by causing cerebral hypoxia followed by loss of muscle tone. Once muscle tone is compromised, increased pressure is applied to both the carotid arteries and the trachea. Direct compression of the carotid arteries also leads to a decrease or loss of cerebral blood flow and brain death. The direct pressure on the carotid sinuses causes a systemic drop in blood pressure, bradycardia, and other arrhythmias. Consequences are anoxic and hypoxic brain injury death.

Ligature-based injuries can include focused force trauma to certain structures. Force applied over a smaller surface area may result in more pointed injuries rather than extensive and broader crush-type injuries. The type of ligature may also be important – barbed ligatures may cause penetrating trauma to various neck zones, and may even injure deep structures. All types of aerodigestive injuries must be considered in these patients. Fractures of the hyoid bones and thyroid cartilage result from a force directed towards these structures.[26]

A variety of spinal cord injuries are associated with strangulation and pathophysiology is directly related to the specific mechanism. Complete cord transection might be a sign of rapid deceleration injuries. Alternatively, injury to surrounding structures may threaten nearby neurological anatomy. Hematomas and injury-related edema have all been described as mechanisms that result in spinal cord trauma. Spinal cord ischemia may result from the disruption of vessels necessary to maintain perfusion. Care must be taken in the evaluation as mechanical forces and displaced surrounding structures may injure or disrupt spinal tendons and ligaments. The pathophysiology of these injuries is diverse and if severe can lead to paralysis and ultimately death.   

Facial and cervical petechiae and ecchymoses are a common injury pattern found in strangulation injuries. Pressure transmitted via compressed vasculature can result in capillary, venule, and arteriole injuries resulting in these skin findings. Facial plethora or swelling can occur due to the externally-applied pressure. Similar mechanisms result in ocular findings such as subconjunctival hemorrhages. Epistaxis from pressure has been described as well and is thought to be due to pressure-related vascular injury.[28]

Vascular trauma may include transection and intimal tears. These injuries can lead to chronic issues and possibly pseudoaneurysms and other vascular complications. Lower pressures are needed to occlude cervical veins, and higher pressure is required for cervical artery deformation. Thrombotic events may result, which can cause acute occlusion and/or embolic phenomenon.[3][26][28]

Histopathology

Histopathological implications of strangulation injuries are as diverse as the pathophysiology that underlies each specific type and the conditions present at the time of injury. Typical findings of anoxic brain injury can be expected. Cell damage can appear in as little as four hours and is dependent on the extent and duration of anoxia/hypoxia. Ischemic cell damage may result in primary necrosis of neurological structures, or a delayed fashion via apoptosis if the patient survives the initial insult. A "cloudy swelling" pattern of nuclear regions and a reduction in basophilic character to the nucleus have been described. Cytoplasmic shrinking and pyknotic nuclei are also potential injury patterns. At the 8-12-hour mark classic “red neurons” begin to appear.[29]

Higher metabolic rate and oxygen demand underscore the areas of the brain that are most easily affected by strangulation injuries. Watershed regions are at a particular risk as well. CA1 pyramidal neurons within the hippocampus are implicated in memory deficits seen in patients who survive. Within the cerebellum, the Purkinje cells are at higher risk of anoxic injury, which explains gait abnormalities sometimes seen in survivors. Arterial border zones in various areas of the brain may demonstrate “wedge-shaped” lesions, which may be seen on detailed neuroimaging as well.[29]

There are multiple forensic pathology considerations in this patient population as well. Excoriation marks on the face and various body surfaces may signal struggle either by the patient to remove a ligature or other object causing strangulation. They may also signify injury caused by a potential assailant. Burns and musculoskeletal trauma may be present on autopsy as well depending on the circumstances. The cause of death can be difficult to assess due to the multiple pathways that lead to the common pathophysiology of death in strangulation. For example, homicide victims who suffer strangulation injuries that were also found submerged in bodies of water might have signs of both strangulation and submersion injury. Both lead to hypoxia and eventually death, and thus determining a sequence of events might be difficult.[3]

Toxicokinetics

Strangulation injuries, whether accidental or intentional may also be compounded by toxicological pathology. Many times alcohol and/or prescription and non-prescription drugs may have been ingested by the patient at or around the time of injury. Many of these substances may also cause central nervous depression and contribute to altered mental status. Underlying life-threatening overdoses with acetaminophen, aspirin, tricyclic antidepressants, and other substances can cause severe metabolic disturbances and complicate strangulation injuries.[3]

History and Physical

The history of a strangulation injury may be obtained from the patient, witnesses, family or friends, first responder personnel, or a combination of the above. Proper history will facilitate proper management. If possible, determine whether the strangulation was a manual, ligature, or hanging injury. When a history of ligature or hanging is elicited, the clinician should further clarify the type of material used. Incomplete versus complete hanging injuries should also be differentiated. If the injury is a complete hanging, the height of the drop should be assessed as this may help prognosticate as well as. Associated injuries and ingestions need to be evaluated. Obtaining an approximate time of injury is also essential, along with a potential duration of the sustained injury. The patient’s initial on-scene presentation, resuscitative efforts initiated, and patient stability or decompensation en route will also aid the practitioner to initiate proper management.

Physical examination may include one or more of the following “hard signs” of strangulation:

Head, Eyes, Ears, Nose, and Throat

• Visual disturbances
• Conjunctival or facial petechial hemorrhages
• Swollen tongue or oropharynx
• Foreign body (blood, vomit, tissue) in the oropharynx
• Facial edema, lacerations, abrasions, ecchymosis
• Neck abrasions, edema, lacerations, or ligature marks
• Tenderness to palpation over the larynx
• Hoarseness or stridor
• Subcutaneous edema or crepitus

Cardiovascular

• Cyanosis or hypoxia
• Arrhythmias
• Respiratory distress
• Crackles or wheezes
• Cough

Neurologic

• Altered mental status
• Seizures
• Stroke-like symptoms
• Incontinence

As with all traumatic injuries, the physical exam must first start with an examination of the airway. Blood, vomitus, sputum, and other foreign bodies may be involved. Audible stridor can result from a threatened upper airway. Auscultation of cervical structures is helpful not only to assess airway patency, but to listen for bruits, thrills, and other signs of vascular injury. The patient's breathing pattern should be noted. Bradypnea and other abnormal breathing patterns may result from Cushing's triad if the patient is showing clinical signs of grave elevations in intracranial pressure. An assessment of the patient's circulatory status is vital. Blood pressure monitoring, capillary refill, and extremity warmth can suggest to the clinician if the patient has signs of spinal shock.[5][25][28][30]

To this end a thorough neurological assessment is vital. Neurological tone, reflexes, and many eponymous findings may suggest upper motor neuron injury or cerebrovascular injury. Care should be taken to assess lateralizing signs as well which may help localize a certain level of spinal cord lesions.

Skin and musculoskeletal findings are likely to be present in severe injuries. Depending on the nature of the trauma a full head to toe assessment should be done for these organ systems. Polytrauma patients may have other injuries that go unrecognized when focused on the immediate needs of the strangulation injury.[28]

In patients where it is appropriate to do so, a rapid psychiatric assessment is necessary. Signs of depression (e.g. depressed mood, suicidal ideations, altered thought content, and many others) may be present. Assessment of the patient’s sensorium, concentration, memory, and other features may point towards concomitant intoxication or concussive head injury.

Evaluation

Once the patient is stabilized, laboratory and radiologic studies can aid in determining the severity of the injury. Laboratory studies may include complete blood count (CBC), CMP, coagulation studies, beta-HCG, toxicology panel (alcohol, drug, aspirin, and acetaminophen levels), lactic acid, and arterial blood gasses. CT is widely available and is the first line of radiologic evaluation of strangulation injuries. CT Angiogram of the carotid and vertebral arteries is the gold standard in care. This allows for the evaluation of vascular and bony structures.[31]

CT of the neck with contrast is less specific than CT Angiogram but will evaluate bony structures and vascular structures to a degree. Non-contrast CT of the brain will evaluate for stroke but is more sensitive for intracranial hemorrhage than for smaller ischemic strokes. A non-contrast CT scan of the brain may identify large areas of infarcted tissue. Non-contrast CT is also the study of choice to evaluate for cerebral edema in the acutely presenting patient.[31]

MRA of the neck is another imaging modality option, although it is less available in smaller and rural centers, and it is also more time-consuming than CT to complete. It is also less sensitive than CTA of the neck in evaluating vessels. MRI of the neck poses similar availability issues. It has less sensitivity than CTA in evaluating vascular structures; however, it is the most accurate study to evaluate the soft tissues of the neck. MRI/MRA of the brain is the most sensitive modality in evaluating both global and anoxic brain injury, ischemic stroke, and, intracranial hemorrhage. Consideration must be given to the patient's clinical stability before pursuing magnetic resonance-based studies.

Carotid doppler is not recommended for the evaluation of strangulation injuries due to its inability to completely evaluate all of the possibly affected vascular structures. Plain chest radiography is also recommended in patients who have required intubation or are in respiratory distress. Bronchoscopy and upper gastrointestinal endoscopy may be indicated later on in the patient’s care. Indications include various signs of aerodigestive injury including hemoptysis and hematemesis.[32]

Treatment / Management

The primary survey, as in any traumatic injury, should begin with an evaluation of the patient’s airway, breathing, and circulation. Immediate resuscitative interventions should take priority over radiologic studies. Clinicians who practice in settings where they are responsible for acute management of patients suffering from strangulation must have extensive experience in airway management, including surgical techniques (emergent tracheostomy and cricothyrotomy).[30](B2)

Patients with "hard signs" or other physical exam findings of extensive cervical injury should immediately have a cervical collar or other immobilization device placed. Removal can only occur once appropriate clinical and radiographic approaches have ruled out unstable fractures, vascular injury, and other threatening pathology. If none of the “hard signs” are present, radiologic studies are not always necessary. After evaluation in the emergency department, the patient may be discharged with strict return precautions. If the patient presents with any of the “hard signs” of strangulation injury, laboratory and radiologic evaluation must be performed.[4][33]

If the radiologic studies are completely negative, disposition should be based on the patient’s clinical condition. Asymptomatic patients may be discharged after Emergency Department evaluation with strict return precautions and in-home monitoring by family or friends. Symptomatic patients with normal radiologic studies should either be admitted to the hospital or the emergency department observation unit, if available, for further monitoring.

Admitted patients require a multidisciplinary approach depending on the extent of their injuries. Delayed pulmonary edema and complications from concomitant musculoskeletal trauma may become of particular importance and thus specialty and organ-specific care must be sought.[34](B3)

Differential Diagnosis

• Anaphylaxis

• Angioedema

• Asthma

• COPD

• Depression and Suicide

• Domestic Violence

• Epiglottitis

• Neck Trauma

• Sexual Assault

• Spinal Cord injuries

Prognosis

Generally, the prognosis for patients who have minimal to no external signs and with unremarkable radiologic workups is favorable. In terms of traumatic sequelae delayed vascular findings are of importance, however with current imaging technology these cases are rare. The prognosis for these patients then becomes a matter of the psychosocial reasons that may have resulted in the injury, and depend on mitigation of exposure.[31]

Severely injured patients, and those with particularly devastating signs of neurological injury, tend to do much worse. Prognosis depends heavily on the extent and duration of anoxic brain injury, and long term recovery depends upon the specific areas of the brain involved. While patients with a low Glasgow Coma Scale tend to do worse, initial neurological conditions do not exclude a favorable recovery. Patients presenting in cardiac arrest tend to have a very grave prognosis.[3][14]