5. CENTRAL NERVOUS SYSTEM

CENTRAL NERVOUS SYSTEM DISORDERS: EPILEPSY, PARKINSON’S DISEASE, ALZHEIMER’S DISEASE, STROKE, AND MIGRAINE: A TEACHER’S COMPREHENSIVE GUIDE

Welcome, future pharmacists and healthcare professionals!

The central nervous system (CNS) is the most complex system in the human body, controlling everything from movement and sensation to memory and emotion. Disorders of the CNS can be devastating, affecting patients’ quality of life and their ability to perform even the simplest tasks. As a pharmacy educator with years of experience teaching pharmacotherapeutics, I have observed that students often find CNS disorders challenging due to their complex pathophysiology and intricate pharmacological management. Let me tell you: Understanding CNS disorders is essential for every pharmacy professional.

In this comprehensive guide, I will walk you through the major CNS disorders—Epilepsy, Parkinson’s Disease, Alzheimer’s Disease, Stroke, and Migraine. I will explain their types, etiology, pathogenesis, clinical manifestations, and both non-pharmacological and pharmacological management. By the end of this article, you will have a thorough understanding of these critical conditions. Let us begin our journey!

Dpharmguru’s exam insights:

CNS disorders are frequently tested in pharmacy exams. Remember: Epilepsy is characterized by recurrent seizures. Parkinson’s Disease involves dopamine deficiency in the substantia nigra. Alzheimer’s Disease is the most common cause of dementia. Stroke is a cerebrovascular accident. Migraine is a recurrent headache disorder. Pay special attention to the pharmacological management of each condition—these are almost always asked in exams!

1. EPILEPSY

Epilepsy forms a group of disorders mainly affecting the nervous system. These disorders are interrelated, having unique characteristics, including a tendency for recurrent seizures, characterized by abnormal discharges of electrical activity in the brain cells. This may result in abnormal behaviors like involuntary muscle movements, unusual perceptions, a disturbed level of consciousness, etc.

According to the WHO, a condition having a tendency for recurrent seizures due to disorder of brain cells is termed epilepsy.

Types of Epilepsy

• Partial Seizures or Psychomotor Epilepsy: Discharge begins locally and remains localised. Symptoms include involuntary muscle contraction, abnormal sensory experiences, autonomic discharge, or effect on mood and behaviour.
• Generalised Seizures: Whole brain is involved, producing abnormal electrical activity in both hemispheres.
• Status Epilepticus: Repeatedly occurring seizures with no recovery in between.
• Myoclonic Seizures: Sudden brief muscle contractions occurring repeatedly in one body part or the whole body.
• Febrile Seizures: Occur mostly in children due to increased body temperature.
• Tonic-Clonic Seizures: Previously referred to as “grand mal” seizures. Include violent muscular spasms and uncontrollable convulsions.
  • Tonic phase: Muscles contract suddenly; person loses consciousness and falls (10-20 seconds).
  • Clonic phase: Muscles contract rhythmically, flexing and relaxing in turn (1-2 minutes).

Etiology of Epilepsy

• Scarring on the brain after a brain injury (post-traumatic epilepsy)
• Stroke (leading cause in individuals more than 35 years of age)
• Lack of oxygen to the brain
• Brain tumour or cyst
• Dementia or Alzheimer’s disease
• Maternal drug use, prenatal injury, brain malformation, or lack of oxygen at birth
• Infectious diseases (AIDS and meningitis)
• Genetic or developmental diseases or neurological diseases

Pathogenesis of Epilepsy

Epileptogenesis is the process by which the previously normal brain is functionally altered and biased towards the generation of abnormal electrical activity promoting chronic seizures. This process occurs in three phases:

• Phase 1: Occurrence of a precipitating injury or event
• Phase 2 (Latent Period): Changes set in motion by the preceding injury transform the previously normal brain into an epileptic brain
• Phase 3: Chronic, established epilepsy

Neurochemical Mechanisms:

• GABA Hypothesis: Reduction of GABA-ergic inhibition results in epilepsy; enhancement of GABA-ergic inhibition results in an anti-epileptic effect
• Glutamatergic Synapses: Play a critical role in all epileptic phenomena; activation of glutamate receptors is pro-convulsant
• Dopamine: Decreased dopamine facilitates appearance of seizures by lowering the threshold triggering such seizures

Clinical Manifestations of Epilepsy

• Recurrent seizures
• Convulsion without fever
• Short blackouts or confused memory
• Intermittent fainting spells
• Temporary insensitivity to instructions or questions
• Sudden stiffness or falling due to unknown reason
• Sudden bouts of blinking without apparent stimuli
• Sudden bouts of chewing due to unspecific reason
• Temporarily seeming dazed and inability to communicate

Non-Pharmacological Management of Epilepsy

• Ketogenic Diet: Used in children with intractable seizures; effective but costly and difficult to follow
• Vagus Nerve Stimulation: Using a programmable pulse generator; effective for refractory seizures (50% reduction in seizures)

Pharmacological Management of Epilepsy

Dpharmguru’s exam insights:

Epilepsy management is frequently tested. Remember: Carbamazepine and Phenytoin are first-line drugs for generalised tonic-clonic seizures. Valproate is first-line for absence and myoclonic seizures. Ethosuximide is specifically used for absence seizures. A common exam question is: “What is the first-line drug for absence seizures?” (Answer: Ethosuximide or Valproate).

2. PARKINSON’S DISEASE (PD)

Parkinson’s Disease (named after its pioneer, James Parkinson in 1817) is a slowly progressive and degenerative disease affecting the nervous system. It results from an insufficiency of dopamine in the brain and is thus categorised as a movement disorder.

According to the WHO, a chronic progressive neurodegenerative disorder of insidious onset, characterised by the presence of predominantly motor symptomatology (bradykinesia, rest tremor, rigidity, and postural disturbances) is termed Parkinson’s disease.

Types of PD

• Based on Etiology:
  • Primary Parkinson’s Disease: Affects individuals after 40 years of age; more prevalent in males
  • Secondary Parkinson’s Disease: Essentially Parkinsonism; results from causes other than PD itself
• Based on Age of Onset:
  • Early Onset Parkinson’s Disease: Before 40 years of age
    • Young-Onset PD: 21-40 years
    • Juvenile PD: Before 20 years
  • Late Onset Parkinson’s Disease: After 40 years of age

Etiology of PD

• Genetic Factors: Mutations in genes result in the occurrence of the disease
• Environmental Factors: Age, sex, dietary habits, infections, environmental toxins like heavy metals and well water
• Other Factors: Head trauma, infections (influenza virus), neoplasms, atherosclerosis, exposure to toxins, drugs like neuroleptics, anti-emetics, and hypertensives

Pathogenesis of PD

PD involves degeneration of the nigrostriatal pathway, thus reducing the neurotransmitter dopamine. Transport of dopamine is impaired, as a result of which excitability of the striatum is altered. The pigment and characteristic black colour of the neurons in the substantia nigra is lost, and some contain Lewy bodies (abnormal protein aggregates made up of α-synuclein protein).

Clinical Manifestations of PD

Primary Symptoms:

• Reduced smelling ability (anosmia)
• Constipation
• Cramped, small handwriting
• Changes in voice
• Stooped position
• Tremor (shaking that occurs at rest)
• Slow motions (bradykinesia)
• Stiffness in arms, legs, and trunk
• Balance issues and a tendency to fall

Secondary Symptoms:

• Blank expression on face
• Tendency to get stuck when walking
• Muffled, low-volume speech
• Decreased blinking and swallowing
• Tendency to fall backward
• Reduced arm swinging when walking
• Parkinsonian gait characterized by stumbling steps when walking

Non-Pharmacological Management of PD

• Physical Therapy: Partial Weight Supported Treadmill Gait Training (PWSTT) and wireless vibratory feedback system
• Physiotherapy: Effective for muscular stiffness and joint discomfort
• Occupational Therapy: Aids in performance of daily activities and promotes freedom
• Speech and Language Therapy: Helps with speech problems in PD

Pharmacological Management of PD

Drugs Acting on Dopaminergic System:

• Dopamine Precursor: Levodopa (L-dopa)—converts to dopamine in the brain
• Peripheral Decarboxylase Inhibitors: Carbidopa, Benserazide—block conversion of levodopa to dopamine in intestine and blood, decreasing nausea and vomiting
• Dopaminergic Agonists: Bromocriptine, Ropinirole, Pramipexole—imitate action of dopamine at dopamine receptor
• MAO-B Inhibitors: Selegiline, Rasagiline—increase and lengthen the effect of every single dopamine molecule
• COMT Inhibitors: Entacapone, Tolcapone—prevent breakdown of levodopa in intestine

Drugs Acting on Cholinergic System:

• Central Anti-cholinergics: Trihexyphenidyl (benzhexol), Procyclidine, Biperiden—block the outcome of a different neurotransmitter
• Anti-histaminics: Orphenadrine, Promethazine—modify the serotonin-histamine system

Dpharmguru’s exam insights:

Parkinson’s Disease management is frequently tested. Remember: Levodopa is the most effective drug but is combined with Carbidopa to reduce peripheral side effects. Dopamine agonists (Bromocriptine, Ropinirole) are used as adjuncts. MAO-B inhibitors (Selegiline) and COMT inhibitors (Entacapone) are also used. A common exam question is: “What is the drug of choice for Parkinson’s Disease?” (Answer: Levodopa + Carbidopa combination).

3. ALZHEIMER’S DISEASE (AD)

Alzheimer’s Disease (AD) is an irreversible, progressive, neurodegenerative disease in which there is severe impairment in cognitive and functional ability of the patient. It is the major cause of dementia and commonly occurs in old age (over age of 65 years). Patients slowly lose their memory, thinking ability, and eventually the ability to carry even the easiest tasks.

Types of AD (Stages)

• Stage 1 (Mild Type): Initial stage, lasts 2-4 years. Patient feels less energetic.
• Stage 2 (Moderate Type): Longest stage, lasts 2-10 years. Patient can perform simple tasks independently but may need assistance with more complicated activities.
• Stage 3 (Severe Type): Memory power worsens or becomes almost non-existent. Patient often sleeps and murmurs. May lose ability to feed themselves, severely impaired speech, loss of ability to recognize people, uncontrolled body functions.

Etiology of AD

• Biochemical Factors: Deficiency of neurochemical agents (Acetylcholine, Norepinephrine, Somatostatin)
• Genetic Factors: Family history of dementia, AD, or other neurodegenerative disorders; Down Syndrome
• Other Factors: Long exposure to metals (manganese or aluminium), vascular diseases, diabetes, midlife hypertension, raised cholesterol, increased fat intake, obesity, smoking

Pathogenesis of AD

Brain tissues of AD patients have three distinctive features:

• Neurofibrillary Tangles: Formed of fibrous proteins in the neurons
• β-Amyloid Plaques: Deposition of protein-like substances
• Granulovascular Changes: Granulovascular degeneration of neurons

Additional Structural Changes:

• Atrophy of cerebral cortex
• Dilation or enlargement of the ventricles
• Reduced brain volume
• Deposition of amyloid around the cortical blood vessels
• Selective loss of cholinergic neurons in pathways to the frontal lobes and hippocampus

Clinical Manifestations of AD

• Loss of memory
• Confusion about events, time and place
• Issues with money management and bill payment
• Trouble performing/taking longer to perform familiar tasks
• Getting lost or wandering
• Personality and behavior changes (agitation, anxiety, unfriendliness)
• Suspicions about family, friends, and caretakers
• Difficulty in recognizing family and friends
• Difficulty in learning and remembering new information
• Difficulty in performing multistep tasks

Pharmacological Management of AD

• Cholinesterase Inhibitors: Donepezil—slow the progression of symptoms; more effective in early stage
• Glutamatergic Agents: Memantine (NMDA receptor blocker)—effective in treating severe AD

Dpharmguru’s exam insights:

Alzheimer’s Disease management is frequently tested. Remember: Donepezil is a cholinesterase inhibitor used in mild to moderate AD. Memantine is an NMDA receptor antagonist used in moderate to severe AD. A common exam question is: “What is the mechanism of action of Donepezil?” (Answer: Cholinesterase inhibition).

4. STROKE

Stroke or Cerebrovascular Accident (CVA) is a condition of hindered flow of blood to the brain due to occlusion or rupturing of blood vessels (haemorrhage). Amount and location of oxygen starvation by the brain tissue or the severity of cerebral bleeding describes the type and extent of neurological impairment.

Types of Stroke

• Ischemic Stroke: Narrowed or blocked arteries reduce blood flow
  • Thrombotic Stroke: Formation of a thrombus in an artery supplying blood to brain
  • Embolic Stroke: An embolus formed in body parts away from the brain is carried to narrow arteries of brain
• Haemorrhagic Stroke: Rupturing or leakage of a blood vessel
  • Intracerebral Haemorrhage: Rupturing of a brain blood vessel spills blood in the surrounding brain tissue
  • Sub-arachnoid Haemorrhage: Rupturing of an artery near the brain surface spills blood in the space between the brain surface and skull

Etiology of Stroke

Modifiable Factors:

• Hypertension, Diabetes mellitus, Hyperlipidemia, Smoking, Inactivity, Obesity, Alcoholism, Sleep apnoea, Estrogen use, Atrial fibrillation, Carotid artery stenosis

Non-Modifiable Factors:

• Increased age, Male gender, Family history, Race (African American > Asian, Hispanic > white), Family history of stroke or heart attack before age 60

Clinical Manifestations of Stroke (FAST)

• F (Face): Does the patient’s one side of the face droop?
• A (Arm): Does one arm drift downward when the patient holds both arms out?
• S (Speech): Is the patient’s speech abnormal or slurred?
• T (Time): It is time to call emergency and get the patient to hospital

Other Symptoms: Dizziness, Loss of balance and coordination, Numbness or paralysis in face, leg, or arm, Blurred or darkened vision, Sudden headache accompanied by nausea, vomiting, or dizziness

Pharmacological Management of Stroke

Ischemic Stroke:

• Emergency Medications: Aspirin (prevents further clotting), Tissue Plasminogen Activator (TPA/Alteplase)—dissolves blood clot
• Other Procedures: Carotid Endarterectomy (surgical removal of plaques), Angioplasty and Stents

Haemorrhagic Stroke:

• Emergency Measures: Warfarin or anti-platelet drugs (Clopidogrel), drugs to lower intracranial pressure and blood pressure
• Surgical Blood Vessel Repair: Surgical Clipping, Coiling (Endovascular Embolisation), Surgical AVM Removal

5. MIGRAINE

Migraine is a recurring type of headache that causes moderate to severe throbbing or pulsing pain, often on one side of the head. Other symptoms include nausea, weakness, and sensitivity to light and sound.

Types of Migraine

• Complicated Migraine (Migraine with Aura): 15-20% of migraine patients experience an aura
• Common Migraine (Migraine without Aura): Occurs without the warning an aura may give
• Silent or Acephalgic Migraine: Includes aura symptom but not the headache
• Hemiplegic Migraine: Causes temporary paralysis or neurological changes on one side of the body
• Retinal or Ocular Migraine: Causes temporary, partial or complete loss of vision in one eye
• Chronic Migraine: Occurs at least 15 days each month
• Migraine with Brainstem Aura: Causes vertigo, slurred speech, double vision, or loss of balance
• Status Migrainosus: Rare and severe type; lasts for more than 3 days

Phases of Migraine

• Prodrome or Pre-Headache Phase: Lasts for a few hours to a few days
• Aura Phase: Lasts for 5-60 minutes
• Headache Phase: Lasts for 4-72 hours
• Post-drome or Migraine Hangover: Lasts for 1-2 days

Clinical Manifestations of Migraine

Prodrome Symptoms: Problem in concentrating, Irritability/depression, Difficulty in speaking and reading, Difficulty in sleeping, Yawning, nausea, fatigue, Sensitivity to light and sound, Food cravings, Increased urination, Muscle tightness

Aura Symptoms: Numbness and tingling, Disturbed vision, Weakness on one side of the body, Speech changes

Headache Symptoms: Pain and stiffness in neck, Depression, giddiness, anxiety, Sensitivity to light, smell and sound, Nasal congestion, Insomnia, Nausea and vomiting

Post-drome Symptoms: Inability to concentrate, Depression, Fatigue, Lack of comprehension, Euphoria

Pharmacological Management of Migraine

OTC Medications: Ibuprofen, Aspirin, Acetaminophen, Naproxen, Caffeine

Prescription Drugs:

• Triptan Class (Abortives): Sumatriptan, Zolmitriptan, Naratriptan
• Calcium Channel Blockers: Verapamil
• CGRP Monoclonal Antibodies: Erenumab, Fremanezumab, Galcanezumab, Eptinezumab
• β-blockers: Atenolol, Propranolol, Nadolol
• Anti-depressants: Amitriptyline, Nortriptyline, Doxepin, Venlafaxine, Duloxetine
• Anti-seizure Drugs: Valproic acid, Topiramate
• Other Drugs: Steroids, Phenothiazines, Corticosteroids

Dpharmguru’s exam insights:

Migraine management is frequently tested. Remember: Triptans (Sumatriptan) are first-line abortive therapy for acute migraine. Prophylactic treatments include β-blockers (Propranolol), anti-depressants (Amitriptyline), and anti-seizure drugs (Topiramate, Valproic acid). A common exam question is: “What is the drug of choice for acute migraine?” (Answer: Sumatriptan).

COMPARISON: CNS DISORDERS

FREQUENTLY ASKED QUESTIONS (FAQs)

1. What is the difference between epilepsy and seizures?

Epilepsy is a chronic condition characterized by recurrent seizures. A seizure is a single episode of abnormal electrical activity in the brain. Not all seizures indicate epilepsy.

2. What is the drug of choice for Parkinson’s Disease?

The drug of choice for Parkinson’s Disease is Levodopa + Carbidopa combination. Levodopa is converted to dopamine in the brain, and Carbidopa prevents peripheral conversion, reducing side effects.

3. What is the difference between Alzheimer’s Disease and other types of dementia?

Alzheimer’s Disease is the most common cause of dementia, accounting for 60-80% of cases. It is characterized by progressive memory loss, neurofibrillary tangles, and β-amyloid plaques. Other types include vascular dementia, Lewy body dementia, and frontotemporal dementia.

4. What is the difference between ischemic and hemorrhagic stroke?

Ischemic stroke is caused by blockage of a blood vessel (thrombus or embolus). Hemorrhagic stroke is caused by rupture or leakage of a blood vessel, leading to bleeding in the brain.

5. What is the drug of choice for acute migraine?

The drug of choice for acute migraine is Sumatriptan (a triptan). Other triptans include Zolmitriptan and Naratriptan.

6. What are Lewy bodies?

Lewy bodies are abnormal protein aggregates made up of α-synuclein protein found in the cells of the substantia nigra in Parkinson’s Disease. They are a characteristic pathological feature of PD.

SUMMARY

Central Nervous System disorders are among the most complex and challenging conditions in medicine. This guide covered the major CNS disorders:

• Epilepsy: Recurrent seizures; managed with anti-epileptic drugs (Carbamazepine, Valproate, Phenytoin)
• Parkinson’s Disease: Dopamine deficiency; managed with Levodopa + Carbidopa, dopamine agonists, MAO-B inhibitors
• Alzheimer’s Disease: Progressive dementia; managed with Donepezil (cholinesterase inhibitor) and Memantine (NMDA receptor antagonist)
• Stroke: Cerebrovascular accident; managed with TPA (ischemic) or surgery (hemorrhagic)
• Migraine: Recurrent headache; managed with Sumatriptan (acute) and Propranolol (prophylaxis)

As I always tell my students: “CNS disorders require a comprehensive understanding of pathophysiology, pharmacology, and patient care. These conditions affect the very essence of who we are—our memories, movements, and perceptions.”

REFERENCES AND FURTHER READING

• Pharmacy Council of India (PCI). (2022). Pharmacotherapeutics Syllabus. New Delhi: PCI.
• Rang, H. P., & Dale, M. M. (2021). Rang & Dale’s Pharmacology (9th ed.). Elsevier.
• Goodman, L. S., & Gilman, A. (2018). Goodman & Gilman’s The Pharmacological Basis of Therapeutics (13th ed.). McGraw-Hill.
• Katzung, B. G. (2021). Basic and Clinical Pharmacology (15th ed.). McGraw-Hill.
• World Health Organization (WHO). (2022). Neurological Disorders. Retrieved from https://www.who.int.
• American Epilepsy Society. (2023). Guidelines for Epilepsy Management.
• Parkinson’s Foundation. (2023). Parkinson’s Disease Treatment Guidelines.
• Alzheimer’s Association. (2023). Alzheimer’s Disease Facts and Figures.
• American Stroke Association. (2023). Stroke Treatment Guidelines.
• American Migraine Foundation. (2023). Migraine Treatment Guidelines.

Disclaimer: This article is for educational purposes only and does not constitute medical advice. Always consult qualified healthcare professionals for medical concerns. Pharmaceutical regulations and guidelines may vary by region—always refer to your local regulatory authorities for specific requirements.

written by:
Dr. N. Sujith Kumar

Dr. N. Sujith Kumar is a pharmacy educator, Pharm.D graduate, and academic content creator from Jawaharlal Nehru Technological University Kakinada (JNTUK), where he completed his Doctor of Pharmacy (Pharm.D) degree between 2015 and 2021. He has more than 7 years of experience creating pharmacy educational content, writing study materials, and reviewing academic articles for pharmacy students. He has also contributed guest articles to pharmacy education platforms, including PharmD Guru. At D.PharmGuru, his work focuses on simplifying complex Diploma in Pharmacy (D.Pharmacy) subjects into easy-to-understand notes, practical explanations, and exam-oriented educational resources for students across India. His areas of focus include Human Anatomy and Physiology, Pharmaceutics, Pharmacology, Pharmaceutical Chemistry, Hospital and Clinical Pharmacy, and other core D.Pharmacy subjects.

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