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Chronic Disorders of Neurologic Function – Vocabulary Review

CNS & PNS Overview

  • Central Nervous System (CNS)
    • Structures: brain and spinal cord.
    • Function: Information processing, integration, higher order functions.
  • Peripheral Nervous System (PNS)
    • All nervous tissue outside CNS.
    • Subdivisions
    • Afferent (sensory) division → carries information to CNS.
      • Somatic sensory receptors: skeletal muscles, joints, skin → position, touch, pressure, pain, temperature.
      • Visceral sensory receptors: cardiovascular, respiratory, digestive, urinary, reproductive organs.
      • Special sensory receptors: smell, taste, vision, balance, hearing.
    • Efferent (motor) division → carries commands from CNS to effectors.
      • Somatic Nervous System (SNS): voluntary control of skeletal muscle.
      • Autonomic Nervous System (ANS): involuntary control.
      • Sympathetic division: “fight-or-flight.”
      • Parasympathetic division: “rest-and-digest.”
    • Effectors: skeletal muscle, smooth muscle, cardiac muscle, glands, adipose tissue.

Brain & Cerebellar Disorders

Seizures & Epilepsy

  • Seizure = transient neurologic event caused by excessive, abnormal neuronal discharges.
  • Epilepsy = recurrent predisposition to seizures.
  • Etiology
    • Anyone can seize under certain circumstances (e.g., fever, toxins).
    • Seizure disorder may be acquired (cerebral injury, infection, metabolic disorder, tumor, stroke).
  • Pathogenesis
    • Altered membrane potential → hyper-excitable, hypersensitive neurons.
  • Clinical manifestations
    • Classification by onset
    • Generalized onset
    • Focal onset
    • Unknown onset
    • Aura/prodrome may precede event.
  • Diagnosis & Treatment
    • History, physical & neurologic exam, \text{EEG}.
    • Pharmacologic therapy, surgery, vagal nerve stimulation, ketogenic diet.

Dementia

  • Progressive deterioration of memory & cognition.
  • Classified as neurodegenerative (e.g., Alzheimer) or non-neurodegenerative (vascular, infectious, metabolic).
  • Alzheimer Disease (AD)
    • Pathogenesis: neuronal degeneration in temporal/frontal lobes → cortical atrophy.
    • Hallmarks: \beta-amyloid plaques, neurofibrillary tangles (NFTs).
  • Vascular Dementia
    • Result of single large CVA, multiple lacunar infarcts, or chronic microvascular ischemia.
  • Clinical Staging of AD
    1. Early (mild): short-term memory loss, word-finding difficulty.
    2. Middle (moderate): disorientation, impaired judgment, wandering.
    3. Late (severe): loss of speech, incontinence, total dependence.
  • Diagnosis & Management
    • Exclude reversible causes (vitamin deficiency, thyroid, drug effects, delirium).
    • Symptom management: cholinesterase inhibitors, NMDA antagonists, behavioral therapy.

Parkinson Disease (PD)

  • Etiology
    • Progressive neurodegenerative disorder; may be idiopathic or acquired (drug-induced, toxins, trauma, infection).
  • Pathogenesis
    • Degeneration of dopaminergic neurons in substantia nigra pars compacta → dopamine deficiency in basal ganglia.
    • Presence of intraneuronal Lewy bodies containing \alpha-synuclein.
  • Clinical Manifestations
    • Bradykinesia/akinesia, resting tremor (often unilateral distal), cogwheel rigidity, postural instability, shuffling gait, masked facies.
  • Treatment
    • Pharmacologic: levodopa/carbidopa, dopamine agonists, MAO-B inhibitors, anticholinergics.
    • Deep brain stimulation, physical therapy, antidepressants.

Cerebral Palsy (CP)

  • Group of non-progressive motor syndromes arising in childhood.
  • Etiology
    • Prenatal maternal infection/disease, perinatal mechanical trauma, postnatal hypoxia, toxins.
  • Clinical Types
    • Spasticity, ataxia, dyskinesia, or mixed.
  • Management
    • Muscle relaxants (baclofen), anticonvulsants, orthopedic surgery, casts/braces, physical & occupational therapy.

Hydrocephalus

  • Abnormal accumulation of cerebrospinal fluid (CSF) in ventricular system.
  • Forms
    • Normal-pressure hydrocephalus (NPH)
    • Obstructive (non-communicating)
    • Communicating
  • Treatment: surgical shunting of CSF (ventriculoperitoneal or ventriculoatrial shunt).

Cerebellar Disorders

  • Cerebellum controls coordination, posture, balance.
  • Etiologies: abscess, hemorrhage, tumors, trauma, viral infection, chronic alcoholism.
  • Manifestations: ataxia, hypotonia, intention tremor, gait & balance disturbance.

Spinal Cord & Peripheral Nerve Disorders

Multiple Sclerosis (MS)

  • Demyelinating disease of CNS; onset typically young adults, higher latitude prevalence.
  • Pathogenesis: immune-mediated demyelination affecting optic/oculomotor nerves & spinal tracts ➔ conduction block.
  • Manifestations: diplopia, weakness, poor coordination, paresthesia, bowel/bladder dysfunction, cognitive deficits.
  • Management: acute steroids, disease-modifying immunotherapies (interferons, monoclonal antibodies), symptomatic treatment.

Spina Bifida

  • Developmental neural-tube defect with incomplete closure of vertebral arch.
  • Types
    • Occulta (no protrusion)
    • Cystica (meningocele, myelomeningocele).
  • Treatment: early surgical repair, ongoing PT/OT, mobility aids.
  • Prevention: folic acid supplementation before conception & during pregnancy.

Amyotrophic Lateral Sclerosis (ALS)

  • Progressive degeneration of upper & lower motor neurons.
  • Manifestations: limb weakness, muscle atrophy, fasciculations, cramps, spasticity, dysphagia, respiratory failure.
  • Diagnosis of exclusion.
  • Management: riluzole, edaravone, NIV ventilation, PEG feeding, multidisciplinary supportive care.
  • Prognosis: mean survival ≈ 3\text{ years} post-diagnosis.

Spinal Cord Injury (SCI)

  • Etiology: trauma (MVAs, falls, violence, sports).
  • Primary damage: compression, transection, contusion.
  • Secondary injury: hemorrhage, edema, ischemia ➔ further neuronal death.
  • Clinical Syndromes
    • Spinal shock: transient loss of reflexes & flaccidity below lesion.
    • Neurogenic shock: hypotension & bradycardia from loss of sympathetic tone.
    • Autonomic dysreflexia: life-threatening HTN triggered by noxious stimulus below lesion >T6.
  • Management: immobilization, surgical decompression/fixation, high-dose methylprednisolone (controversial), respiratory support, rehabilitation.

Guillain–Barré Syndrome (GBS)

  • Acute immune-mediated polyradiculoneuropathy, often post-infectious.
  • Variants: AIDP, AMAN, AMSAN, Miller Fisher.
  • Pathogenesis: cross-reactive antibodies → demyelination/axonal damage of peripheral nerves.
  • Manifestations: ascending weakness starting in legs, areflexia, possible respiratory failure.
  • Treatment: supportive care, IVIG or plasmapheresis, DVT prophylaxis, rehabilitation.
  • Prognosis: majority recover (weeks to months).

Facial Nerve Palsy / Bell Palsy

  • Idiopathic unilateral CN VII paralysis; often viral-linked (HSV).
  • Manifestations: sudden facial droop, inability to close eye, decreased lacrimation, hyperacusis, absent nasolabial fold.
  • Course: self-limited (days-weeks).
  • Treatment: eye protection (artificial tears, patch), corticosteroids, antivirals (controversial), physical therapy.

NGN Case Study – C7 Spinal Injury Rehabilitation

  • Expected functional gains at C7 level
    • Excellent bed mobility (due to intact elbow extension via triceps, strong wrist extensors).
    • Independent transfers to wheelchair.
    • Good shoulder movement enabling ADLs.
    • Performs most grooming tasks without assistance.
  • Less likely/Not expected
    • Independent self-catheterization (hand intrinsic weakness).
    • Need for assisted pulmonary hygiene (diaphragm innervation intact at C3-C5).
    • Reliance on electric wheelchair (manual wheelchair typically feasible).
    • Assistance for self-feeding (adaptive devices rarely needed at C7).

Key Numerical / Anatomical References

  • C3\,–\,C5: phrenic nerve, diaphragmatic breathing.
  • C7: elbow extension, wrist flexion/extension, partial finger extension.
  • Mean ALS survival \approx 3\;\text{years}.
  • Node of Ranvier: gap between myelin segments enabling saltatory conduction.
  • Anatomical loci in PD: substantia nigra, putamen, posterior hypothalamus, amygdala, olfactory bulb.

Integrative & Ethical Considerations

  • Early diagnosis & multidisciplinary care improve quality of life in chronic neurologic diseases.
  • Preventive strategies (folic acid, vaccinations) can reduce incidence of congenital anomalies & post-infectious neuropathies.
  • Ethical obligation to balance aggressive interventions with patient autonomy and expected benefit (e.g., shunts, DBS, ventilatory support).
  • Caregiver support & societal resources crucial for progressive disorders (AD, ALS, SCI).