Penetrating head injury

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Joanna Ekabua, M.D. [2]

Synonyms and keywords:: Penetrating head injury

Overview

A penetrating head injury, or open head injury, is a life-threatening condition in which the dura mater, is breached and there is a foreign body in the brain. Penetrating injury can be caused by high-velocity projectiles such as bullets or objects of lower velocity such as knives, or bone fragments from a skull fracture that are driven into the brain. A perforating head injury is one in which the object passes through the head and leaves an exit wound. Although penetrating head injuries can be dramatic in appearance and presentation, the trajectory is of particular importance the case of gunshot wounds. Immediate neurosurgical consulting mandatory.

Classification

Penetrating head injury can be classified as

• Non-missile type
• Missle type

Pathophysiology

• Though it is more likely to cause infection, penetrating trauma is similar to closed head injury such as cerebral contusion or intracranial hemorrhage in a number of ways. As in closed head injury, intracranial pressure is likely to increase due to swelling or bleeding, potentially crushing delicate brain tissue. Most deaths from penetrating trauma are caused by damage to blood vessels, which can lead to intracranial hematomas and ischemia, which can, in turn, lead to a biochemical cascade called the ischemic cascade. The injury in penetrating brain trauma is mostly focal (affects a specific area of tissue). Sometimes in penetrating injuries, the brain releases thromboplastin, which can lead to problems with clotting.
• In penetrating injury from high-velocity missiles, injuries may occur not only from initial laceration and crushing of brain tissue by the projectile but also from the subsequent cavitation. High-velocity objects create centrifugal forces and can create a shock wave that cause stretch injuries, forming a cavity that is three to four times greater in diameter than the missile itself. A pulsating temporary cavity is also formed by a high-speed missile and can have a diameter thirty times greater than that of the missile. Though this cavity is reduced in size once the force is over, the tissue that was compressed during cavitation remains injured. Destroyed brain tissue may either be ejected from entrance or exit wounds or packed up against the sides of the cavity formed by the missile.
• Low-velocity objects usually cause penetrating injuries in the regions of the skull's temporal bones or orbital surfaces, where the bones are thinner and thus more likely to break. Damage from lower-velocity penetrating injuries is restricted to the tract of the stab wound because the lower-velocity object does not create as much cavitation. However, low-velocity penetrating objects such as slow bullets may ricochet inside the skull, continuing to cause damage until they stop moving.

Causes

Common causes of penetrating head injury

• Angle grinders
• Nail Gun
• Metal drill
• Gunshot wounds

Differentiating Penetrating Head Injury from other Diseases

Penetrating head injury must be differentiated from

• Traumatic brain injury
• Head injury
• Skull fracture

Epidemiology and Demographics

The highest-velocity injuries tend to have the worst associated damage. Penetrating injury from any missile such as a bullet has a mortality rate of 92%. Thus, firearms cause the most head injury-related deaths. Perforating injuries have an even worse prognosis.

Penetrating head trauma can cause loss of abilities controlled by parts of the brain that are damaged. A famous case of penetrating head trauma was that of Phineas Gage, whose personality drastically changed after he sustained a penetrating injury to his frontal lobe.

Up to 50% of patients with penetrating brain injuries get late-onset epilepsy.

Diagnosis

Diagnostic Study of Choice

History and Symptoms

The hallmark of penetrating head injury is finding

• Anhedonia in patients with right ventrolateral injury

Physical Examination

• Glasgow Coma Scale (GCS)
  • GCS 8-15 and somnolence: Sleepy, easy to wake
  • GCS 8-15 and stupor: Hypnoid, hard to wake
  • GCS ≥ 13: Mild Head Injury
  • GCS 9–12: Moderate Head Injury
  • GCS ≤ 8: Severe Head Injury
  • GCS 7-8: Light coma; Coma Grade I
  • GCS 5-6: Light coma; Coma Grade II
  • GCS 4: Deep coma; Coma Grade III
  • GCS 3: Deep coma; Coma Grade IV

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Laboratory Findings

Electrocardiogram

X-ray

Ultrasound

CT Scan

MRI

Other Imaging Findings

Other Diagnostic Studies

Treatment

Medical Therapy

Surgery

Primary Prevention

Secondary Prevention