Nervous System Diseases

Nervous System Diseases

Overview of the Nervous System

• Central Nervous System (CNS): Consists of the brain and spinal cord.
• Peripheral Nervous System (PNS): Includes peripheral nerves and nerve plexus.
• Structure of the CNS:
  • Cerebrum: Largest part of the brain responsible for higher brain functions.
  • Cerebellum: Coordinates voluntary movements and balance.
  • Brain Stem: Connects brain to spinal cord and controls involuntary functions.
  • Spinal Cord: Contains neural pathways for communication.
• Meninges: Protective membranes covering the brain and spinal cord. Includes:
  • Dura Mater: Outer durable layer.
  • Arachnoid Mater: Middle web-like layer.
  • Pia Mater: Innermost delicate layer.

Microbial Diseases of the Nervous System

• Types of Pathogenic Microbes:
  • Infect cells in the nervous system (e.g., encephalitis, meningitis).
  • Release toxins affecting neurons (e.g., botulism, tetanus).
• Common Microbial Diseases:
  • Encephalitis
  • Meningitis
  • Leprosy

Bacterial Diseases of the Nervous System

Bacterial Meningitis

• Signs & Symptoms:
  • Sudden high fever, severe headache, vomiting, light sensitivity.
  • Stiff neck, altered muscle control, back spasms.
• Pathogens & Virulence Factors:
  • Streptococcus pneumoniae: Leading cause in adults; treated with penicillin.
  • Neisseria meningitidis: Common in adolescents; transmission via droplets, prevented by vaccines (Menactra, Menomune).
  • Haemophilus influenzae: Causes illness in children; prevented by Hib vaccine.
  • Listeria monocytogenes: Affects fetuses & immunocompromised; found in undercooked foods.
  • Streptococcus agalactiae (Group B): Causes neonatal meningitis; prevention via prophylactic antibiotics during birth.

Encephalitis

• Definition: Infection of the brain; can lead to severe behavioral changes or death.
• Symptoms can develop rapidly, within hours to days.

Diagnosis and Prevention

• Diagnosis: Based on symptoms and culturing bacteria from cerebrospinal fluid (CSF) during a spinal tap.
• Prevention: Vaccinations available, such as for S. pneumoniae, H. influenzae, and N. meningitidis.

Hansen’s Disease (Leprosy)

• Forms:
  • Tuberculoid leprosy: Non-progressive.
  • Lepromatous leprosy: Progressive tissue destruction.
• Pathogen: Caused by Mycobacterium leprae; transmitted via nasal secretions.
• Symptoms: Loss of sensation, tissue loss, and disfigurement due to long-term infection.
• Treatment: Long-term antimicrobial therapy (dapsone, rifampin).

Botulism

• Symptoms: Flaccid paralysis, diplopia, dysphagia.
• Pathogen: Clostridium botulinum; causes intoxication from the toxin found in improperly stored foods.
• Treatment: Involves washing the intestinal tract and administering botulism immune globulin (BIG).
• Prevention: Proper food handling and storage.

Tetanus

• Symptoms: Rigid paralysis (often of jaw), headaches, irritability.
• Cause: Clostridium tetani found in contaminated wounds.
• Prevention: Vaccination (DTAP, DT, TD) every 5-10 years.

Viral Diseases of the Nervous System

Viral Meningitis

• Signs & Symptoms: Similar to bacterial meningitis but milder; usually self-limiting.
• Pathogens: Enteroviruses most common; others include echovirus, herpesvirus.
• Diagnosis: Lack of bacteria in CSF; specific treatment does not exist, prevention through hygiene.

Poliomyelitis

• Conditions: Asymptomatic, minor polio, nonparalytic, and paralytic forms exist.
• Pathogen: Poliovirus; transmitted via contaminated water.
• Vaccine: Salk vaccine introduced in 1954

Rabies

• Symptoms: Agitation, hallucinations, paralysis, aggressive outbursts.
• Pathogen: Rabies virus spread through bites from infected animals.
• Prevention: Immediate post-exposure prophylaxis with antibodies and vaccination.

Arboviral Encephalitis

• Transmission: Through mosquitoes; symptoms similar to meningitis.
• Prevention: Limiting mosquito exposure, vaccines available for horses.

Fungal and Protozoan Diseases

Cryptococcal Meningitis

• Pathogen: Cryptococcus neoformans; affects immunocompromised individuals, predominantly.
• Treatment: Amphotericin B and flucytosine.

Primary Amebic Meningoencephalopathy (PAM)

• Pathogen: Naegleria fowleri; enters through the skin or mucous membranes, especially during exposure to warm freshwater.
• Treatment: Limited effectiveness; high fatality rate (90%).

Prion Disease

• Definition: Infectious proteins, causing spongiform encephalopathies (e.g., Mad Cow Disease).
• Transmission: Can occur through consumption of infected meat.
• Symptoms: Causes brain lesions leading to severe neurological decline.