7th+ed

Chapter 17: Disorders of the Central and Peripheral Nervous Systems and Neuromuscular Junction

Traumatic Brain Injury (TBI)

• Alteration in brain function resulting from external forces such as:

  • Motor vehicle accidents

  • Falls

  • Unintentional blunt trauma

• Types of TBI:

  • Primary Injury:

    • Direct impact (focal - closed or open, or diffuse injury)

  • Secondary Injury:

    • Indirect consequences of the primary injury, including systemic and brain tissue responses.

Closed Brain Injury

• Characterized by grossly observable brain lesions:

  • Occurs when a head strikes a surface or an object strikes the head.

  • The dura mater remains intact, shielding the brain from external exposure.

• Injury Locations:

  • Coup Injury: Directly beneath the impact point.

  • Contrecoup Injury: Opposite side of the impact.

• Common injuries include:

  • Contusions

  • Subdural hematomas

  • Epidural hematomas

  • Intracerebral hemorrhage

Open Brain Injury

• Dura mater is broken; cranial contents are exposed to the environment.

• Involves both focal and diffuse injuries:

  • Example causes: Compound skull fractures and missile injuries.

Diffuse Brain Injury (Diffuse Axonal Injury - DAI)

• Widespread damage throughout the brain.

• Defined clinically by coma lasting between 6 to 24 hours post-TBI.

• Caused by acceleration/deceleration or rotational forces leading to:

  • Shearing, tearing, or stretching of nerve fibers.

• Severity is correlated with the shearing force applied to the brainstem.

Secondary Brain Injury

• Results indirectly from primary injury:

  • Includes trauma and stroke syndromes, systemic processes (e.g., hypotension, hypoxia), and cerebral processes (e.g., inflammation, edema).

• Management focuses on preventing hypoxia and maintaining cerebral perfusion pressure.

Categories of TBI

• Mild TBI:

  • Short or no loss of consciousness and confusion lasting minutes.

• Moderate TBI:

  • Loss of consciousness for 30 minutes to 6 hours, confusion, and amnesia lasting over 24 hours.

• Severe TBI:

  • Loss of consciousness for over 6 hours and severe cognitive defects.

Complications of TBI

• Postconcussion Syndrome:

  • Symptoms last weeks or months; managed with observation.

• Posttraumatic Seizures:

  • Occur soon after injury; prevention initiated for moderate to severe TBI.

• Chronic Traumatic Encephalopathy:

  • Progressive brain disease due to repeated injuries, leading to violent behaviors, depression, and cognitive/motor changes.

Spinal Cord Injury

• Primary Injury:

  • Mechanical trauma and immediate tissue destruction; can occur without vertebral fractures.

• Secondary Injury:

  • A pathophysiologic cascade (hemorrhages, inflammation) that occurs after injury, which may be life-threatening in the cervical region.

Vertebral Injuries

• Result from acceleration, deceleration, or deformation forces.

• Classified as:

  • Simple fractures

  • Compressed (wedged) fractures

  • Comminuted (burst) fractures

  • Dislocations.

Mechanisms of Vertebral Injuries

• Include:

  • Osteophytes

  • Disruption of intervertebral disks

  • Spinal cord compression and ligament compression.

Manifestations of Spinal Cord Trauma

• Spinal Shock:

  • Loss of all spinal cord activity at and below the injury; results in flaccid paralysis and absent reflexes.

• Neurogenic Shock:

  • Happens with injury above T6, leading to blood pressure drops and impaired sympathetic activity.

• Autonomic Hyperreflexia:

  • Sudden reflex sympathetic discharge, causing hypertension and other complications,

  • Triggered by sensory stimuli below the lesion level.

Degenerative Disorders of the Spine

• Low Back Pain:

  • 80% of the population may experience it; most cases are idiopathic.

  • Categories include acute, chronic (e.g., cauda equina syndrome).

• Degenerative Joint Disease:

  • Includes degenerative disk disease and structural defects like spondylolysis and spondylolisthesis.

  • Herniated Intervertebral Disk:

  • Caused by displacement of disk materials; common in trauma or degenerative diseases.

Cerebrovascular Disease (CVD)

• Any abnormality in the brain caused by blood vessel processes, often resulting in ischemia or hemorrhage.

• Types of Stroke:

  • Ischemic (thrombotic and embolic)

  • Hemorrhagic

  • Cryptogenic (undetermined origin).

Intracranial Aneurysm

• A dilation or ballooning of a cerebral vessel due to weakness in the vessel wall.

• Classified as:

  • Saccular (berry)

  • Fusiform (giant) aneurysms.

Potential Complications of Meningitis

• Bacterial Meningitis:

  • Caused by bacteria crossing the BBB, leading to serious infectious symptoms requiring rapid treatment.

• Viral Meningitis:

  • Milder than bacterial, limited to the meninges.

• Fungal Meningitis:

  • Rare compared to other types; can lead to significant neurological symptoms.

Multiple Sclerosis (MS)

• A chronic progressive immune-mediated inflammatory disease damaging myelin, leading to:

  • Paresthesia, weakness, cognitive impairments.

• Contains four subtypes based on progression patterns.

Guillain-Barré Syndrome

• An acquired inflammatory disease leading to demyelination of peripheral nerves, typically following respiratory or GI infections, usually resolves over weeks to months.

Peripheral Nervous System Disorders

• Injury to peripheral nerves by various processes can result in neuropathy, including:

  • Mononeuropathies (single nerve)

  • Polyneuropathy (generalized involvement).

  • Myasthenia Gravis:

    • An autoimmune disorder affecting transmission at the neuromuscular junction, leading to muscle weakness.

Central Nervous System Tumors

• Primary brain tumors include various types of gliomas, meningiomas, and metastatic tumors.

• Spinal cord tumors can also be classified into intramedullary and extramedullary tumors, which present with compressive and irritative symptoms.