Penetrating head injury
Synonyms and keywords::  Penetrating head injury

# Overview
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. Although penetrating head injuries can be dramatic in appearance and presentation, the trajectory is of particular importance the case of gunshot wounds. Penetrating head injury can cause loss of abilities controlled by parts of the brain that are damaged. Risk factors for penetrating head injury include violence, accidents, and suicide attempts. Some complications include Infection, abscess formation, cerebrospinal fistula, neuroendocrine dysfunction, cerebrospinal fluid leak, traumatic intracranial aneurysm, dural venous sinuses thrombus, and bullet fragment migration. Diagnosis is made by physical and neurologic exams, CT scan, and MRI.  Immediate neurosurgical consulting mandatory in all cases of penetrating head injuries. Compared to close head injuries, penetrating head injuries carries a worse prognosis.

# Historical Perspective
- There is limited knowledge on the historical perspective of penetrating head injury.
- Penetrating head injury secondary to stabbing through the cranium was first published in 1800.

# Classification
- Penetrating head injury may be classified into 2 main groups based on messile type
Non-missile type
Missle type
- Non-missile type
- Missle type
- Wounds resulting from penetrating brain injury can be classified into five categories
Tangential
Penetrating
Perforating
Ricochet
Careening.
- Tangential
- Penetrating
- Perforating
- Ricochet
- Careening.

# Pathophysiology
- The pathophysiology of penetrating head injury is due to injury to neuronal and vascular structures which is mostly focal. This injury leads to release of thromboplastin, which can lead to problems with clotting, infection, swelling or bleeding, potentially crushing delicate brain tissue. If severe, brain herniation can occur.   Most deaths from penetrating trauma are caused by damage to blood vessels, leading to intracranial hematomas and ischemia as early as 30 minutes after the initial injury. This can, in turn, lead to a biochemical cascade called the ischemic cascade.
- 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.
- 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.

# Causes
Common causes of  penetrating head injury
- Angle grinders
- Nail Gun
- Metal drill
- Bullets
- Key
- Metal strip

# 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 incidence of penetrating head injury has increased over the last decade with an estimated 35,000 civilian deaths annually.
- Patients of all age groups may experience penetrating head injury.
- There is no racial predilection to penetrating head injury.
- Penetrating head injury affects men and women equally.

# Risk Factors
Common risk factors in the development of penetrating head injury include
- Violence
- Accidents
- Explosions/blast
- Suicide attempts

# Screening
There is insufficient evidence to recommend routine screening for penetrating head injury.

# Natural History, Complications, and Prognosis
- If left untreated, 100% of patients with penetrating head injury die.
- Common complications of penetrating head injury
Intracranial infections/cerebral abscess, most common cause staphylococcus aureus
Local wound infection. Most common causes are wood splinters and bone fragments
Cerebral vasospasm in the presence of subarachnoid hemorrhage
Up to 50% of patients with penetrating brain injuries get late-onset epilepsy
Traumatic intracranial aneurysm/pseudoaneurysm
Meningitis
Ventriculitis
Hyponatremia
Cerebral edema
Cerebral contusions
Elevated intracranial pressure
Intraventricular hemorrhage
Cerebrospinal fistula
Neuroendocrine dysfunction
Cerebrospinal fluid leak
Hematomas
Arteriovenous fistulas
Dural venous sinuses thrombus
Bullet fragment migration
Neurological deficits
copper or Lead toxicity from retained bullet fragments
Death
- Intracranial infections/cerebral abscess, most common cause staphylococcus aureus
- Local wound infection. Most common causes are wood splinters and bone fragments
- Cerebral vasospasm in the presence of subarachnoid hemorrhage
- Up to 50% of patients with penetrating brain injuries get late-onset epilepsy
- Traumatic intracranial aneurysm/pseudoaneurysm
- Meningitis
- Ventriculitis
- Hyponatremia
- Cerebral edema
- Cerebral contusions
- Elevated intracranial pressure
- Intraventricular hemorrhage
- Cerebrospinal fistula
- Neuroendocrine dysfunction
- Cerebrospinal fluid leak
- Hematomas
- Arteriovenous fistulas
- Dural venous sinuses thrombus
- Bullet fragment migration
- Neurological deficits
- copper or Lead toxicity from retained bullet fragments
- Death
- Prognosis is generally good with early decompressive craniectomy in non bullet penetrating objects. 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.About 70-90% of penetrating head injury victims die before arriving the hospital, and 50% of those who survive to the hospital die during resuscitation attempts in the emergency department.
The following clinical factors have been associated with poor outcomes
- Low post-resuscitation glasgow coma scale
- Older age
- Large and unreactive pupils
- Asymmetric Pupil
- Hypoxia, and hypotension (Systolic blood pressure <90 mmHg).
Other factors include
- Time to reach neurosurgeon
- Weapon ballistics, including
Caliber
Proximity to the projectiles source.
- Caliber
- Proximity to the projectiles source.

# Diagnosis
Diagnostic Study of Choice
- There are no established criteria for the diagnosis of penetrating head injury.
History and Symptoms
The hallmark of penetrating head injury is finding
- Headache
- Vomiting
- Confusion
- Weakness of extremities
- Loss of consciousness
- Seizure
- Anhedonia in patients with right ventrolateral injury
Physical Examination
Common physical examination findings of penetrating head injury include
- Penetrating object in the skull.
- Neurologic deficit
Motor and sensory skills
Hearing and speech
Coordination and balance
Mental status
Mood or behavior changes
- Motor and sensory skills
- Hearing and speech
- Coordination and balance
- Mental status
- Mood or behavior changes
- Normal to abnormal Glasgow Coma Scale (GCS). GCS is considered to be the best single predictor of good or bad outcome following penetrating head injury. Survival rate is 0-8.1%, 35.6% and 90.5% for GCS scores of 3-5, 6-8 and 9-15 respectively
GCS 8-15 and somnolence: Sleepy, easy to wake
GCS 8-15 and stupor: Hypnoid, hard to wake
GCS  13: Mild Head Injury
GCS 912: 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
- GCS 8-15 and somnolence: Sleepy, easy to wake
- GCS 8-15 and stupor: Hypnoid, hard to wake
- GCS  13: Mild Head Injury
- GCS 912: 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
Laboratory Findings
- There are no diagnostic laboratory findings associated with penetrating head injury.
Electrocardiogram
- There are no ECG findings associated with penetrating head injury.
X-ray
An x-ray may be helpful in the diagnosis of penetrating head injury
Ultrasound
- There are no ultrasound findings associated with penetrating head injury.
CT Scan
Head CT scan is helpful in the diagnosis of penetrating head injury. CT scan shows the foreign object.
MRI
Cranial MRI may be helpful in the diagnosis of penetrating head injury.
- MRI can be dangerous in cases of retained ferromagnetic objects as it can move in response to the magnetic torque.
Other Imaging Findings
- There are no other imaging findings associated with penetrating head injury.
Other Diagnostic Studies
- There are no other diagnostic studies associated with penetrating head injury.

# Treatment

## Medical Therapy
- Penetrating head injury is a medical emergency and requires prompt treatment.
- Aggressive resuscitation has been associated with improved survival.
Correction of  hypotensionand hypoxia
Airway maintenance
Control of  hemorrhaging
Hyperosmolar therapy with mannitol or hypertonic saline
Correction of traumatic coagulopathy
Placement of a cervical immobilization device
- Correction of  hypotensionand hypoxia
- Airway maintenance
- Control of  hemorrhaging
- Hyperosmolar therapy with mannitol or hypertonic saline
- Correction of traumatic coagulopathy
- Placement of a cervical immobilization device
- Treatment of penetrating head injury aims at controlling bleeding, intracranial pressure, and preventing infections.
Ceftriaxone
1 g IV 0.5 to 2 hours prior to surgery.
4 g/day IV divided every 12 to 24 hours; maximum 4 g/day
Metronidazole
Loading Dose: 15 mg/kg infused over one hour (approximately 1 g for a 70-kg adult).
Maintenance Dose: 7.5 mg/kg infused over one hour every six hours (approximately 500 mg for a 70-kg adult). The first maintenance dose should be instituted six hours following the initiation of the loading dose.
Anticonvulsant
Antitetanic vaccine
Analgesics
- Ceftriaxone
1 g IV 0.5 to 2 hours prior to surgery.
4 g/day IV divided every 12 to 24 hours; maximum 4 g/day
- 1 g IV 0.5 to 2 hours prior to surgery.
- 4 g/day IV divided every 12 to 24 hours; maximum 4 g/day
- Metronidazole
Loading Dose: 15 mg/kg infused over one hour (approximately 1 g for a 70-kg adult).
Maintenance Dose: 7.5 mg/kg infused over one hour every six hours (approximately 500 mg for a 70-kg adult). The first maintenance dose should be instituted six hours following the initiation of the loading dose.
- Loading Dose: 15 mg/kg infused over one hour (approximately 1 g for a 70-kg adult).
- Maintenance Dose: 7.5 mg/kg infused over one hour every six hours (approximately 500 mg for a 70-kg adult). The first maintenance dose should be instituted six hours following the initiation of the loading dose.
- Anticonvulsant
- Antitetanic vaccine
- Analgesics

## Surgery
Surgery is the mainstay of treatment for penetrating head injury. Procedures used are 
- Craniectomy with dura mater plasty
- Craniotomy
Both procedures have been shown to have similar morbidity and mortality. Optimum outcomes have been reported with early decompressive craniectomy.

# Prevention

## Primary Prevention
Effective measures for the primary prevention of penetrating head injury include
- An effective measure for the primary prevention of penetrating head injury are helmets
- Use seat health while driving

## Secondary Prevention
- There are no established measures for the secondary prevention of penetrating head injury.