TOPIC : Blunt Force Cranio-cerebral Injuries
Sub topics:
· The anatomy of the scalp, skull, meninges and the surface of the brain
· Coup and contre-coup contusions
· The intra-cranial hemorrhages
· Blunt force fractures of the cranio-facial skeleton
Notes for the topic: Scalp has five layers from outside to inwards: skin, connective tissue, galea aponeurotica, loose areolar tissue, and pericranium (periosteum). Skull is a diploic bone having an outer table and inner table. The meningeal membranes covering the brain inside the cranial cavity consist of the dura mater, arachnoid mater and piamater. Dura mater is penetrated by bridging veins (emissary veins) along the vertex. Coup contusions occur at the site of impact injury to the head and produced by compression of the brain due to inward bending of the bone. Contre-coup contusions occur 180 degree opposite the point of impact and are most common in the frontal and temporal lobe. Intra-axial haemorrhage is bleeding within the brain itself examples are intraparenchymal haemorrhage and intraventricular haemorrhage. Extra-axial haemorrhage, bleeding that occurs within the skull but outside of the brain tissue, falls into three subtypes : epidural, subdural and subarachnoid hemorrhage. Most of the injuries to facial bones are related to the application of blunt force trauma on the face. Injury to the skull mainly comprise of fractures which are dependent on various factors, such as: violence acting / force of the active blows or passive impact, site of injury on the skull age of the victim.
The anatomy of the scalp, skull, meninges and the surface of the brain
Scalp is the outermost covering of the head and is continuous with the skin of the face and has five layers from outside to inwards: skin, connective tissue, galea aponeurotica, loose areolar tissue, and pericranium (periosteum). Skull is a diploic bone having an outer table and inner table. The outer table is thicker and stronger, while the inner table is thinner and weaker. The spongy (often marrow-containing) bone in between is known as the diploe and gives greater elasticity to the bone . In children and babies the sutures have not united and thus there is even much larger lendency to give way between bones. These sutures may also spring open in head injuries in adolescents. The meningeal membranes covering the brain inside the cranial cavity consist of the dura mater, arachnoid mater and piamater . Dura mater is the strong and gray/bluish connective tissue membrane and is firmly attached to the skull, penetrated by bridging veins (emissary veins) along the vertex. Polypoid invaginations of dura penetrate the inner walls of venous sinuses, especially the sagittal sinus to form "arachnoid granulations." The arachnoid mater is a thin, vascular meshwork-like membrane beneath dura. Sheaths of arachnoid follow vessels into the brain as they penetrate into the neural surface. These vessels and thin strands of connective tissue anchor the brain within subarachnoid space. This space is filled with cerebrospinal fluid and the width of the space varies from less than one millimeter in young to a centimeter or more in the old, in whom cerebral atrophy has developed. This means that bridging vessels are longer and more vulnerable to shearing and rotatory stress. The pia mater is not a true membrane, but is inseparable from underlying brain.
Coup and contre-coup contusions:
Coup contusion: These contusions occur at the site of impact injury to the head and produced by compression of the brain due to inward bending of the bone. They are less common than contre-coup contusions. Coup contusion are associated with the blow to the head with minimal contre-coup contusion. If both contusions are are present, then a line drawn between their centers will indicate the direction of force relative to the head.
Contre-coup contusions: Contre-coup contusions occur 180 degree opposite (directly opposite) the point of impact and are most common in the frontal and temporal lobe. They are produced by the head in motion impacting a stationary object, and thus, they are classically associated with falls from standing height in which the head impacts broad flat rigid surface.
A fall on the left side of the occiput would is expected to produce contre-coup contusions in,the right frontal and temporal Jobes. A fall on the top of the head would produce contusions on the inferior surface of the cerebrum. Even though individuals frequently fall on their faces, contrecoup contusions are almost never seen in the occipital lobes.
The intra-cranial hemorrhages
Intracranial haemorrhage includes haemorrhage occurring within the cranial cavity. Fracture of the skull bones, though is the common cause of intracranial haemorrhage, the haemorrhage can occur even without fracture of any of the skull bone, or in absence of any injury to the brain, may be due to disease process. A detailed history of past illness, and detailed autopsy may be the answer to various questions that often arise in case of death from head injuries. Haemorrhage resulting directly from trauma usually occurs over the surface of the brain, but deep-seated haemorrhage can also occur in the cerebrum, cerebellum or brain stem, due to trauma. The intracranial haemorrhage is usually accompanied with contusions or lacerations of the brain as coup or contracoup injuries. Common causes of intracranial haemorrhages are as diseases like aneurysms, arteritis, blood disorders, neoplasm, trauma to the skull, brain or its membranes, and effects of injury upon already existing disease. Intra-axial haemorrhage is bleeding within the brain itself examples are intraparenchymal haemorrhage and intraventricular haemorrhage. Extra-axial haemorrhage, bleeding that occurs within the skull but outside of the brain tissue, falls into three subtypes:
Epidural haemorrhage – is caused by trauma, and results from laceration of most commonly the middle meningeal artery. This is a very dangerous type of injury because the bleed is from a high pressure arterial system and deadly increase in intracranial pressure can result rapidly. Patients have a loss of consciousness then a lucid interval, then sudden deterioration. A lenticular (convex) deformity in the head CT is diagnostic of this condition.
• Subdural haemorrhage results from tearing of the bridging veins in the subdural space between the dura and arachnoid mater. Head CT shows crescent-shaped deformity.
• Subarachnoid haemorrhage, like intraparenchymal haemorrhage, can result either from trauma or from rupture of aneurysms or arteriovenous malformations Blood is seen layering into the brain along sulci and fissures, or filling cisterns (most often the suprasellar cistern ). The classic presentation of subarachnoid haemorrhage is the sudden onset of a severe headache. This can be a very dangerous entity, and requires emergent neurosurgical evaluation, and sometimes urgent intervention.
Blunt force fractures of the cranio-facial skeleton:
Injuries to the Facial Bones: Most of the injuries to facial bones are related to the application of blunt force trauma on the face. Blunt force trauma includes – blow with blunt weapons such as stick, fist etc or by fall from height over the face which can bring about fracture of the facial bones such as: nasal bones (frequently) ,ethmoidal bones (with more force) ,maxilla , mandible. A heavy blow on the jaw can drive the condyles against the base of the skull, producing a fissured fracture.
Cranial bone fractures: Injury to the skull mainly comprise of fractures which are dependent on various factors, such as: violence acting / force of the active blows or passive impact, site of injury on the skull age of the victim. Blunt force on the occiput, mostly as a consequence of a fall on the back of head, frequently causes independent fractures of anterior cranial fossa such as cracks of the thin orbital roofs (secondary fractures at the site of the countrecoup). Longitudinal fractures of the base of the skull frequently occur due to fall on occiput. Sequence of skull injuries may be determined by Puppe’s rule. According to this rule, a later fracture does not cross a pre-existing fracture line but terminates on reaching the fracture line of the earlier fracture (Fig.17.2C. Skull fractures are of two types and they are:
a) Fracture of the vault of the skull : Types are listed below
Fissured fracture • Depressed fracture • Comminuted fracture (crushed fracture) • Stellate fracture (Radiating fracture) • Mosaic fracture • Elevated fracture/suture line fracture • Gutter fracture • Perforating fracture • Pond fracture (Indented fracture) • Cut fracture • Combined fracture
b) Fracture of base of the skull: Fracture of base of the skull includes following subtypes • Fracture of the anterior cranial fossa • Fracture of the middle cranial fossa • Fracture of the posterior cranial fossa • Fracture around foramen magnum • Hinge fracture. • Longitudinal fracture of base of the skull.
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