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Air rifle injury to the oropharynx. The essential role of computed tomography in deciding on surgical exploration
  1. T Hung,
  2. P Huchzermeyer,
  3. A E Hinton
  1. Department of Otolaryngology, St George's Hospital, London
  1. Correspondence to: Mr Terry Hung, Senior House Officer, 16 St Clements Mansions, Lillie Road, Fulham, London SW6 7PG (e-mail: 113302.3310{at}compuserve.com)

Abstract

Gunshot wounds specific to the oropharynx are extremely rare with no reported cases of such injury in the world literature. The importance of such cases rests on the use of modern imaging techniques including computed tomography, magnetic resonance imaging, and vascular imaging in the making of management decisions and particularly in deciding the need for exploration of such an injury. In our case a conservative approach was adopted in view of the computed tomography finding and the stable clinical condition of the patient.

  • oropharynx
  • gunshot wound

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Gunshot injuries and fatalities are common in the United States where the firearm regulations are more lenient than those of the UK. However there has been a surge of gunshot incidents in the UK in recent years when increasing violence in the media and the deinstitutionalisation of mental patients were contributory factors. Air rifles may be possessed without a certificate in the UK if they are not of type declared dangerous by the Firearms Rules 1969. An air rifle should discharge a pellet with a kinetic energy below 16.3 J (12 ft lb). Above these levels the weapon is classified as a firearm under section 1 of the Firearm Act 1968. Air rifle injuries can range from trivial to fatal depending on the site of injury and the vascular damage. The majority of entry wounds reported in the literature are external. We report the first case in which our patient has an intraoral entry wound. The use of emergency computed tomography was essential in the localisation of the pellet and the formulation of a management plan.

Case report

A 22 year old man claimed to have accidentally triggered his air rifle, which was aiming at his open mouth. He sustained a gunshot wound to his oropharynx. There was a minimal amount of bleeding from his oral cavity. He did not complain of any breathing difficulty. He complained only of discomfort of the left side of his throat and neck.

He looked remarkably calm on arrival at the accident and emergency department. There was no stertor or stridor. His cardiovascular status was stable. His oxygen saturation was 99% on air throughout the admission. There was minimal swelling and tenderness of the left upper anterior triangle of his neck. Surgical emphysema was not elicited. A 1 cm entry wound was noted at the middle portion of the anterior faucial pillar. Flexible pharyngoscopy revealed a bloodstained tongue base but no active haemorrhage. The airway was completely patent.

The soft tissue neck radiograph showed a radio-opaque pellet just anterior to the base of the odontoid peg (figs 1 and 2). The emergency computed tomogram of the neck showed the metallic pellet lying in the prevertebral soft tissues anterior to the transverse process of the second cervical vertebra (fig 3). The pellet was found to lie within 1 cm of and medial to the left internal carotid artery.

Figure 1

Lateral soft tissue neck radiograph showing the pellet anterior to the odontoid peg.

Figure 2

Posteroanterior neck radiograph showing the pellet in the anterolateral soft tissue of the neck.

Figure 3

Contrast enhanced computed tomogram showing the metallic pellet (large arrow) lying to the left of the midline in the prevertebral soft tissue anterior to the transverse process of the axis (small arrow shows left internal carotid artery).

The patient was treated with intravenous cefotaxime and metronidazole prophylactically. Oral intake was started after 24 hours of close observation. He was discharged on the third day in view of satisfactory aerodigestive function. The decision was made against retrieval of the pellet by surgical exploration as the procedure could be more hazardous than the risks of leaving the pellet undisturbed The patient was reviewed after two months without any sequelae. As the pellet was thought to be an iron alloy, he was warned against entering any strong electromagnetic field including magnetic resonance scanning. He will be treated expectantly if complications arise.

Discussion

It is estimated that one person each year dies from an air powered weapon injury in the UK.1 Fatalities and injuries are most commonly accidents, but deliberately inflicted injuries do occur. Airguns are dangerous weapons when inappropriately handled and should not be considered as toys. Basic ballistics verifies that a projectile's potential to disrupt tissue is determined by both its mass and its velocity. Modern day pneumatic rifles allow the generation of muzzle velocities of up to 350 feet per second. Speeds of 150 feet per second and 200 feet per second are required for skin penetration and bone penetration, respectively.2 A pressure wave follows the projectile with the creation of a “temporary cavity” which could have a significant wounding mechanism. Inelastic tissues such as liver are far more susceptible to disruption by the temporary cavity than are more flexible body tissue such as muscle, bowel wall, and lung.3 Nichols and Sens used cytological technique to analyse direct ballistic trauma in several tissue type, most notably in muscular tissue.4 Progressive damage to skeletal and cardiac muscle was seen in multiple preparations. This ranged from partial separation of the fascicles to cytoplasmic homogenisation and nuclear rupture.

Most of the world literature described external gunshot wounds of the head, chest, abdomen, and the extremities. Only two bizarre and fatal cases of gunshot injuries involving the human orifices were reported, namely intrarectal and intranasal routes.5, 6 Both patients described had past psychiatric history. Our patient is the first case recorded with gunshot injury via an intraoral route and he denied such a past psychiatric history.

The first priority in the management of gunshot injury to the head and neck region should always be the securing of the airway, breathing, and circulation. There is little disagreement in the literature about how to treat penetrating projectile wounds of the chest and abdomen or those that disrupt major blood vessels or bone. Ironically, most of the dispute concerns treatment of the least lethal injuries and how to manage the soft tissue disruption.

Pathology of the oropharynx, unlike their external counterpart is notoriously difficult to visualise in the emergency situation. Systemic signs are only a rough guide to the progression of complications. Acute radiological evaluation of gunshot wounds has been established in other organs.7 Imaging is most important in the definitive management of gunshot injuries to the head and neck. The soft tissue neck radiograph is only a rough guide to the anatomical position of the pellet. It reveals insufficient details of the soft tissue anatomy. Computed tomography allows much more accurate localisation of the pellet in respect to the important anatomical structures. In fact Milroy et al had successfully located both the pellet and the fragments using computed tomography.1 Contrast enhancement allows relatively precise localisation of the pellet in respect of the main blood vessels, the left internal carotid artery in our case. The use of emergency computed tomography was essential as it gave us reassurance of the integrity of the vasculature and it allowed us to adopt a conservative management approach in this emergency senario.

The decision of non-retrieval of the pellet on a definitive basis was an exercise of risk management. Surgical access of the oropharynx will require the commando approach when mandibulectomy is performed.8 This procedure has a very high morbidity.

References

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Footnotes

  • Conflict of interest: none.

  • Funding: none.

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