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).