Neurological Dysfunctions

NEUROLOGICAL DYSFUNCTIONS

CHAPTERS: 33-34-35

Plan:

  • Brain Anatomy and Physiology (A/P)

  • Medical Disorders affecting the CNS

  • Brain Cancer and Tumors

  • Trauma to Nervous System

  • Other Disorders affecting Brain Function

Neuroanatomy and Neurophysiology

Central Nervous System (CNS)

  • Comprises the brain and spinal cord.

Peripheral Nervous System (PNS)

  • Comprising cranial nerves and spinal nerves.

Spinal Cord

  • Motor neurons descend to effectors.

  • Sensory neurons ascend to the brain.

Classification of Neurons

  • Upper Neurons: Located within the brain.

  • Lower Neurons: Located in the spinal cord.

Major Brain Structures

  • Thalamus: Relay center for sensory and motor signals to the cerebral cortex.

  • Hypothalamus: Regulates autonomic functions and hormones.

  • Pituitary Gland: Releases hormones that regulate various physiological processes.

  • Pons: Connection between different parts of the nervous system, including the cerebellum.

  • Brainstem: Controls basic life functions, such as breathing and heartbeat.

  • Medulla Oblongata: Maintains vital body functions, including heart rate and breathing.

  • Cerebrum: Responsible for higher brain functions such as thought and action.

  • Cerebellum: Coordinates voluntary movements and maintains posture and balance.

Neuroanatomy and Tracts
Corticospinal Tract

  • Composed of upper motor neurons that descend into the spinal cord.

  • Contralateral (80%): Neurons cross over to the opposite side of the body.

  • Ipsilateral (20%): Neurons remain on the same side.

  • Decussation: Occurs in the brainstem where the crossover takes place.

Corticobulbar Tract

  • Runs parallel to corticospinal tract, involved in controlling muscles of the face, head, and neck.

Spinothalamic Tract

  • Transmits sensory information from the periphery to the brain.

  • Crossover: Occurs at some level within the spinal cord.

  • Cerebral injury presentations often show effects on the opposite side of the body.

Cerebrovascular Circulation

  • Head arteries:

    • Internal carotid arteries

    • Middle cerebral artery

    • Anterior cerebral artery

    • Posterior cerebral artery

    • Basilar artery

    • Vertebral arteries

  • Circle of Willis: An arterial circle supplying blood to the brain and surrounding structures.

Signs and Symptoms of Seizures

  • General Symptoms:

    • Confusion, aura, sudden falls, staring episodes, uncontrollable jerking movements, strange sensations and emotions.

    • Loss of consciousness or awareness.

Components of Brain Function by Lobes

  • Temporal Lobe:

    • Understanding language, behavior, memory, hearing.

  • Brainstem:

    • Controls breathing, blood pressure, heartbeat, alertness/sleep.

  • Occipital Lobe:

    • Responsible for vision and color perception; for example, color blindness.

  • Cerebellum:

    • Maintains balance and coordination.

Seizures Definition and Types

  • Seizures defined as:

    • Uncontrolled, sudden electrical neuronal discharge in the brain causing transient alteration in brain function.

    • A single, temporary event interrupts normal brain function.

    • Structural abnormalities are the most common cause in adults.

Causes of Seizures

  • Trauma, hypoglycemia, electrolyte disorders (e.g. hyponatremia), acidosis, infections/fever, tumors, chemical ingestion (medications, illicit drugs, alcohol), substance abuse withdrawal, malformations, genetics.

Types of Seizures

  • Generalized Seizures:

    • Clonic: Rhythmic jerking.

    • Tonic: Muscle stiffening for 20-30 seconds.

    • Tonic-Clonic: Body stiffening with repeated jerks and loss of consciousness.

    • Atonic: Loss of normal muscle tone; risk of falling.

    • Absence: Brief lapses in consciousness, appearing to stare.

    • Myoclonic: Brief jerks or twitches, conscious during event.

  • Focal Seizures:

    • Simple: No loss of consciousness.

    • Complex: Altered consciousness.

Clinical Features of Seizures

  • Clonic seizures involve rhythmic jerking and lead to a limp state, often include cyanosis and excessive drooling, with possible oral injuries (biting tongue).

  • Urinary incontinence and lack of memory of the event are common.

Focal Seizure Specifics

  • Frontal Lobe:

    • Jacksonian seizure: Tingling in hand or arm.

    • Adversive seizures: Eyes or head turn to one side.

  • Temporal Lobe:

    • Strange sensory experiences (smell/taste), altered behavior, déjà vu, lip-smacking, or chewing movements.

  • Occipital Lobe:

    • Symptoms include flashing lights, spots, and vomiting.

Etiology of Seizures

  • Common Causes:

    • Head trauma, strokes (especially in the elderly), brain neoplasms, congenital malformations, and degenerative brain disorders (e.g. Alzheimer’s disease).

    • Environmental stimuli (e.g. blinking lights), genetic predisposition, infections, metabolic disturbances (e.g. hypoglycemia, hyponatremia), withdrawal from substances.

Terms Related to Seizures

  • Postictal Period: Confusion or fatigue after a seizure, leading to deep sleep.

  • Aura: A unique, pre-seizure sensation often involving strange lights or smells and confusing thoughts.

Epilepsy and Classification

  • Epilepsy: Chronic neurological disorder characterized by recurrent seizures without an underlying correctable cause.

  • Diagnosis: Traditional diagnosis requires 2 unprovoked seizures at least 24 hours apart, indicating a predisposition toward seizures.

Status Epilepticus

  • Defined as 30 minutes of continuous seizure activity or two or more sequential seizures without full consciousness between seizures.

  • Considered a medical emergency due to the risk of brain injury or function loss, and may lead to respiratory or cardiovascular failure.

Treatment of Epilepsy

  • Medications include antiepileptic agents that modify ion channels or neurotransmitter activity in the brain, e.g., Phenytoin, Valproic Acid, Carbamazepine.

  • Goal to decrease seizure risk while limiting adverse side effects.

Headaches Overview

  • Types of Headaches:

    • Tension Headaches (Muscular): Occur as band-like pain in the occipital or frontal regions.

    • Migraine Headaches (Vascular): Often severe, unilateral, involving nausea, photophobia, can be accompanied by an aura, may last 1-3 days.

    • Cluster Headaches (Vascular): Unilateral pain with severe intensity, occurs around the eye and may include autonomic phenomena (tearing, nasal symptoms).

Tension Type Headaches (TTH)

  • Symptoms include band-like pain around head and associated neck stiffness, common with a stable headache pattern over time.

  • Triggers may include muscle tension, anxiety, flexion-extension neck injury, or poor posture.

Treatment for TTH

  • Over-the-counter medications (e.g., NSAIDs, acetaminophen), relaxation techniques, regular exercise.

Migraine Headaches

  • Precipitating factors include emotional stress, specific foods, hormone changes, lack of sleep, flickering lights.

  • Characterized by throbbing pain, nausea, photophobia, and can be debilitating with motor activity worsening symptoms.

Migraine Pathophysiology

  • Decreased serotonin and increased levels of calcitonin gene-related peptide (CGRP) suspected to play a role in migraines.

  • CGRP known to be a vasodilator.

Treatment of Migraines

  • NSAIDs, serotonin receptor agonists (triptans), dopamine receptor antagonists, or preventive treatments (botulinum injections).

Multiple Sclerosis (MS)

  • Characterized by demyelination of the nerve fibers in the brain and spinal cord, resulting in patchy degeneration of nerves.

  • Symptoms involve a combination of sensory and motor dysfunction.

Chronic Demyelinating Disorder

  • Progressive with remissions and exacerbations.

  • Unknown etiology, but autoimmune components believed to be significant.

Risk Factors for MS

  • Include genetic predisposition, viral infections, environmental factors (colder climates), with females being affected more.

  • Common symptoms include fatigue, visual disturbances, muscle weakness, and gait disturbances.

Four Types of MS

  1. Relapsing-Remitting MS: Characterized by clear periods of exacerbation with full or partial recovery.

  2. Secondary Progressive MS: Follows the relapsing-remitting course with progressive worsening.

  3. Progressive-Retreating MS: Gradual progression with some relapses.

  4. Primary Progressive MS: Steady progression from onset.

Diagnosis of MS

  • Made via MRI showing lesions of demyelination; confirmed by symptomatology and lumbar puncture to rule out other conditions.

  • Examples include Lyme disease or systemic infections.

Clinical Manifestations of MS

  • Include fatigue, cognitive impairment, visual disturbances (e.g., nystagmus), gait issues, spasticity, bladder dysfunction, and sensory loss.

Parkinson's Disease

  • A neurodegenerative disorder characterized by loss of dopamine-producing cells in the substantia nigra.

  • Onset typically occurs between ages 40 to 70, more common in men.

Key Characteristics

  • Symptoms include tremors, rigidity, bradykinesia, and postural instability leading to a mask-like facial expression, with progressive motor control impairment.

  • Progression of the condition can lead to cognitive decline and changes in autonomic function.

Diagnosis of Parkinson's Disease

  • Utilizes the TRAP criteria: Tremor at rest, Rigidity, Akinesia, Postural instability. No laboratory tests confirm diagnosis.

  • Treatments include Levodopa (L-dopa) with carbidopa; however, long-term use may result in diminished efficacy.

Guillain-Barré Syndrome (GBS)

  • An acute inflammatory demyelinating polyneuropathy leading to variations in motor weakness and paralysis due to an autoimmune response, often post-viral infection.

Symptoms of GBS

  • Numbness, paresthesia, muscle weakness, reflex loss, potential respiratory compromise with an ascending symmetric weakness pattern.

Risk Factors

  • Possibly autoimmune, may be preceded by mild respiratory or intestinal infection. Minimal muscle atrophy is common.

Amyotrophic Lateral Sclerosis (ALS)

  • Lou Gehrig's disease, a rapidly progressing and fatal condition characterized by complete degeneration of motor neurons and muscle weakness.

  • Initial symptoms include muscle cramps, weakness, and changes in coordination leading to full paralysis while sensation remains intact.

Diagnosis and Symptoms of ALS

  • Diagnosed through clinical findings showing involvement of both upper and lower motor neurons and specific patterns of weakness.

  • Symptoms escalate to encompass all voluntary musculature, including respiratory failure.

Myasthenia Gravis (MG)

  • An autoimmune disorder affecting the acetylcholine receptors at the neuromuscular junction, leading to variable muscle weakness.

  • It typically presents with ocular symptoms, such as diplopia and ptosis, progressing to generalized weakness.

Treatment Options

  • Include Acetylcholinesterase inhibitors, IV immune globulin, and the possibility of a thymectomy.

Trigeminal Neuralgia

  • Characterized by sudden unilateral facial pain due to dysfunction of the trigeminal nerve (CN V), typically presenting in short episodes.

Presentation and Treatment

  • Pain is often described as stabbing or electric shock-like, affecting women more typically.

  • Treatment may involve medications aimed at managing neuropathic pain.

Bell's Palsy

  • A sudden onset of unilateral facial nerve paralysis, leading to asymmetry and inability to control facial muscles. The etiology is often viral.

Symptoms of Bell's Palsy

  • Inability to raise eyebrows, drooping eyelids and corners of the mouth, sensitivity to sound, and potential pain around the jaw.

  • Treatment involves corticosteroids and antivirals, aiming for recovery typically within 6 months.

Meningitis & Encephalitis

Meningitis

  • Inflammation of the meninges surrounding the brain and spinal cord.

  • Bacterial Meningitis: Medical Emergency!

  • Viral Meningitis: More common, symptomatic management.

Symptoms of Meningitis

  • Severe headache, fever, altered mental status, photophobia, and neck stiffness.

  • Diagnosis established via lumbar puncture and CSF analysis showing cloudy appearance in bacterial vs. clear in viral.

Alzheimer's Disease

  • Most common form of dementia characterized by brain tissue degeneration and associated with amyloid plaques and neurofibrillary tangles.

  • Symptoms include amnesia, cognitive impairment, and change in personality.

  • Onset of symptoms generally after age 65, with risk factors including family history and lifestyle factors linked to cardiovascular health.

Sundowning Effect

  • Agitation and confusion that occurs in the late afternoon/evening.

Delirium

  • A transient and usually reversible form of cerebral dysfunction, marked by fluctuating symptoms and decreased attention span.

  • Evidence of underlying precipitating factors is critical in management and prevention.

  • Treatments primarily focus on addressing the underlying causes.

The provided notes on neurological dysfunctions offer various examples and details regarding conditions and their symptoms, which can lead to issues such as 'trips' (falls or gait disturbances).

For instance, in Seizures, a key symptom can be "sudden falls" (Atonic seizures specifically cause a loss of normal muscle tone and a risk of falling). Multiple Sclerosis (MS) symptoms include "gait disturbances," which can lead to unsteady movement and falls. In Parkinson's Disease, patients experience "postural instability" as a core characteristic, making them prone to falls. Similarly, Guillain-Barré Syndrome (GBS) is characterized by "muscle weakness" and "reflex loss," which can significantly impair balance and cause falls. Amyotrophic Lateral Sclerosis (ALS) also leads to "muscle weakness" and "changes in coordination," heightening the risk of falling as the disease progresses.

These examples illustrate how specific neurological dysfunctions directly impact motor control, balance, and consciousness, contributing to falls or difficulty walking.