Concussion and OtherTraumatic Brain Injuries¶

Chapter 454 | Part 13: Neurologic Disorders · Part 13 – Neurologic Disorders · Chapter 454

Key Clinical Points¶

TBI is defined as an alteration in brain function or evidence of brain pathology caused by external force, characterized by (1) loss/decreased level of consciousness (LOC), (2) memory loss (retrograde or posttraumatic), (3) neurologic deficits, and/or (4) mental state alterations.
GCS scores range from 3 to 15; severity is graded as Mild (13-15), Moderate (9-12), and Severe (3-8).
Epidural hematomas typically arise from middle meningeal artery injury, often feature a 'lucid interval' before deterioration, and appear lenticular on CT.
Subdural hematomas are primarily venous; acute ones are crescentic, while chronic ones (common in elderly/anticoagulant users) may be isodense or hypodense.
Diffuse Axonal Injury (DAI) involves axonal shearing and is visualized on MRI (gradient-echo) as hemosiderin deposits.
Basilar skull fractures are associated with hemotympanum, Battle sign (mastoid ecchymosis), and raccoon sign (periorbital ecchymosis).
Concussion (mTBI) accounts for 70–90% of treated TBIs; 3T MRI can identify microhemorrhages or contusions in these patients.
Traumatic SAH is common in TBI and serves as an objective imaging biomarker, especially in mTBI.
Contusions are parenchymal bruises (coup or contrecoup) resulting from displacement/compression of the brain.
Epidural hematomas occur in up to 10% of severe head injuries; one-third of patients with subdural hematomas may have a lucid interval.

DEFINITION & OVERVIEW¶

• Definition: TBI is defined as an alteration in brain function, or other evidence of brain pathology, caused by an external force, and characterized by: ◦ (1) Any period of loss or decreased level of consciousness (LOC). ◦ (2) Any loss of memory for events immediately before (retrograde) or after (posttraumatic) the injury. ◦ (3) Any neurologic deficits. ◦ (4) Any alteration in mental state at the time of injury. • Evidence of TBI: Can include visual, neuroradiologic, or laboratory confirmation; however, it is more often diagnosed on the basis of acute clinical criteria. • GCS Scoring System: ◦ Most recognized method for grading TBI severity. ◦ Assessment includes motor function, verbal responses, and eye opening. ◦ Range: 3 to 15. ◦ Clinical Note: Patients should be described by the three components (e.g., E3V4M6); total scores are primarily used for characterizing groups. • Severity Classification: ◦ Mild TBI (mTBI): GCS 13–15. ◦ Moderate TBI: GCS 9–12. ◦ Severe TBI: GCS 3–8. • TBI Mechanisms: ◦ Direct hit by object, head striking an object, acceleration/deceleration movement, penetrating foreign body, or forces from blast/explosion. ◦ Common causes include falls and motor vehicle crashes (more common in men); other causes include motorcycle, bicycle, skateboarding, and pedestrian injuries.

EPIDEMIOLOGY¶

• Prevalence: ◦ US: 2.5 to 4.8 million cases per year. ◦ Global: At least 10 million serious enough for death or hospitalization. • Economic Impact: ◦ Global burden: $400 billion annually. ◦ US cost: >$76 billion annually. • Long-term Impact: ◦ 5.3 million Americans live with significant disabilities from TBI. ◦ Increased awareness of military and sports-related TBI highlights lifelong consequences for previously 'dismissed' injuries. • Clinical Management: ◦ Requires education on natural history and treatment of acute symptoms (e.g., headache). ◦ Follow-up is essential to identify/treat persistent postconcussion symptoms (PPCS) such as headache, balance issues, depression, and sleep disorders.

ETIOLOGY & PATHOPHYSIOLOGY¶

• Concussion (mTBI): ◦ Represents 70–90% of all treated TBIs. ◦ Often presents with normal CT; however, 3T MRI can identify contusions and microhemorrhages. ◦ 'Complicated mTBI' refers to cases with concurrent CT/MRI abnormalities (more likely to have unfavorable outcomes). • Skull Fracture: ◦ Indicates site and severity of injury. ◦ Risk: Potential for meningitis (if arachnoid membrane is torn) or CSF leakage (causing severe orthostatic headache). • Basilar Fractures: ◦ Associated with hemotympanum, Battle sign (mastoid ecchymosis), and raccoon sign (periorbital ecchymosis). • Epidural Hematoma: ◦ Source: Typically middle meningeal artery rupture following skull fracture. ◦ Clinical Feature: Often accompanied by a 'lucid interval' of minutes to hours before deterioration. ◦ Incidence: Occur in up to 10% of cases of severe head injury. ◦ Imaging: Lenticular-shaped hemorrhage on CT. • Subdural Hematoma (Acute): ◦ Source: Primarily venous; can occur with minimal trauma in elderly or those on anticoagulants. ◦ Clinical Feature: May present with unilateral headache and dilated pupil. ◦ Incidence: Up to one-third of patients may have a lucid interval before coma. ◦ Imaging: Crescentic shape on CT. • Subdural Hematoma (Chronic): ◦ Timing: Develops days/weeks after injury; common in elderly with age-related atrophy. ◦ Imaging: Isodense or hypodense crescentic clots; may show a vascular fibrous capsule on contrast study. • Traumatic Subarachnoid Hemorrhage (SAH): ◦ Common in TBI; often seen in sulci. ◦ Significance: In mTBI, serves as an objective imaging biomarker for injury. • Contusion: ◦ Definition: Surface bruise of the brain (petechial hemorrhage, edema, tissue destruction). ◦ Mechanism: Coup (at point of impact) or Contrecoup (antipolar area during deceleration). ◦ Severity: Trauma causing prolonged unconsciousness usually produces some degree of contusion. • Axonal Injury: ◦ Diffuse Axonal Injury (DAI): Involves shearing of axons; visible on MRI (gradient-echo) as hemosiderin deposits.

DIAGNOSTIC APPROACH¶

Initial Clinical Assessment: • Evaluate GCS components: Eye Opening (E), Verbal Response (V), and Best Motor Response (M). • Timing: Assess before sedatives or intubation to ensure accurate scoring.
Imaging Selection: • Standard CT: Primary tool for identifying acute epidural/subdural hematomas and large contusions. • 3T MRI: Utilized for detecting microhemorrhages, axonal injury (DAI), and evaluating patients with normal CT but clinical symptoms. • Gradient-echo / SWI: Specific sequences used to identify hemosiderin deposits in TAI/DAI.
Basilar Fracture Identification: • Battle sign → Mastoid ecchymosis. • Raccoon sign → Periorbital ecchymosis. • Hemotympanum → Blood behind the tympanic membrane.

MANAGEMENT & TREATMENT¶

Acute Epidural Hematoma: • Action: Rapid surgical evacuation and ligation/cautery of the damaged vessel (typically middle meningeal artery).
Acute Subdural Hematoma: • Small/Stable: Clinical observation with serial imaging. • Large/Deteriorating: Emergency craniotomy for evacuation.
Chronic Subdural Hematoma: • Management: Surgical evacuation through burr holes (with cranial drain). • Complex cases: Craniotomy required if fibrous membranes are present to prevent recurrence.
Concussion Follow-up: • Action: Identify and treat PPCS (headache, balance issues, depression, sleep disorders) via multidisciplinary care team.

KEY PEARLS & HIGH-YIELD POINTS¶

• GCS Interpretation: Use the three components (E, V, M) for individual patients; total scores are less informative and used primarily for group comparison. • Epidural vs. Subdural: Epidural = Lenticular/Middle Meningeal Artery; Subdural = Crescentic/Venous. • Lucid Interval: Characteristic of epidural hematomas (not always present in subdural). • DAI Detection: Often CT-negative but visible on MRI (gradient-echo) as hemosiderin deposits. • Basilar Fracture Signs: Hemotympanum, Battle sign, and raccoon sign are key indicators of basilar fracture.

Reference Tables¶

TABLE 454-1 Glasgow Coma Scale¶

Harrison's 22e, p.3571

EYE OPENING (E)		VERBAL RESPONSE (V)
Spontaneous	4	Oriented	5
	3	Confused
To pressure	2	Words	3
	1	Sounds
		None
Best Motor Response (M)
Obeying commands	6
	5
Normal flexion	4
	3
Extension	2
	1

TABLE 454-2 Review of Concussion Symptoms PHYSICAL Headaches Dizziness Nausea and/or vomiting Noise sensitivity Sleep…¶

Harrison's 22e, p.3575

PHYSICAL	COGNITIVE	BEHAVIORAL
Headaches	Forgetfulness or poor memory	Being irritable, easily angered
	Poor concentration
Nausea and/or vomiting	Taking longer to think	Feeling frustrated or impatient
Sleep disturbance
Blurred vision
Double vision