8 - Nervous System

bone

protects brain and spinal cord

meninges

3 protective membranes surrounding cns

cerebrospinal fluid

cushion which provides the nutrients for NS

Microglial cells

help defend NS against pathogens

Blood brain barrier

protect brain by restricting passage of large, non-lipid soluble, highly charged particles

Transcellular mechanism

mechanism where bacteria adhere to the epithelial cells and are translocated across these barriers by processes such as pinocytosis or receptor-mediated endocytosis

paracellular mechanism

1. Involves the invasion of CNS following disruption of tight junctions between the cells, resulting in increased permeability. This can occur at:

   • Choroidal epithelial cell junction

   • Endothelial cell junction in veins

   • Within the subarachnoid space in cells of the arachnoid membrane

trojan horse mechanism

The bacteria may travel with infected leukocytes, such as macrophages, allowing them to cross into the CNS

Lumbar puncture at L3-L4 interspace

Diagnosis of bacterial meningitis

Waterhouse-Friderichsen syndrome

complication of meningococcal meningitis

Kernig’s sign

Resistance to full extension of leg at knee when hip is flexed

Brudzinski’s sign

involuntary lifting of legs when lifting a patient’s neck from supine position

PCV13, PPV23

vaccine for pneumococcal meningitis

MPSV4, MCV4

vaccine for pneumococcal meningitis

Hib conjugate vaccine

vaccine for haemophilus meningitis

tetanospasmin

potent neurotoxin which binds to target sits on peripheral motor neurons which may be carried to central neurons in the spinal cord and cleave proteins involved in the release of the inhibitory neurotransmitters

spatula test — Touch the posterior pharyngeal wall with a spatula → Reflex spasm of masseters → Biting (negative result: Gag reflex)

diagnosis of tetanus

DTaP vaccine, Tdap vaccine (in ph: DPT and Td vax)

Tetanus vaccination

DESCRIPTION	S/X
Droplets or close and prolonged contact   Inflammation of membranes of the spinal cord or brain	Fever, headache, stiff neck, N/V, altered mental status, resistance to full extension of leg and knee

CONDITION	CAUSATIVE AGENT	TREATMENT
Bacterial meningitis	Haemophilus influenzae, Neisseria meningitidis, Streptococcus pneumoneae	Empiric therapy (Vancomycin + 3rd gen Cephalosporin) + adj Dexamethasone

DESCRIPTION	S/X
Most serious form of meningitis	Rash that does not fade when pressed

CONDITION	CAUSATIVE AGENT	TREATMENT
Meningococcal meningitis	Neisseria meningitidis	3rd gen Cephalosporin
		Prophy: Ciprofloxacin / Ceftriaxone
		Vaccine: serotype A,C,Y,W-135

DESCRIPTION	S/X
	May cause pneumonia, otitis media and epiglottitis

CONDITION	CAUSATIVE AGENT	TREATMENT
Haemophilus meningitis	Haemophilus influenzae	3rd gen Cephalosporin
		Vaccine: Hib conjugate vaccine

DESCRIPTION	S/X
Leading cause of bacterial meningitis	May cause pneumonia, otitis media

CONDITION	CAUSATIVE AGENT	TREATMENT
Pneumococcal meningitis	Streptococcus pneumoniae	Vancomycin + 3rd gen Cephalosporin

DESCRIPTION	S/X
Ingestion of contaminated food products -> invasion via intestinal mucosa	Healthy = mild infection, non specific Immunocompromised = meningitis and septicemia Pregnant = transplacental infection

CONDITION	CAUSATIVE AGENT	TREATMENT
Listeriosis	Listeria monocytogenes

DESCRIPTION	S/X
Enter through breaks in skin due to release of exotoxin	Hyperexcitability and autonomic dysfunction   Lock jaw, stiff neck, sardonic smile, spasm of back muscle

CONDITION	CAUSATIVE AGENT	TREATMENT
Tetanus	Clostridium tetani
		Tetanus immunoglobulin Metronidazole Systemic = diazepam or lorazepam

DESCRIPTION	S/X
Exotoxin in food or water is ingested and travels to skeletal muscles	Descending, symmetric, flaccid paralysis; difficulty swallowing, droopy eyelids

CONDITION	CAUSATIVE AGENT	TREATMENT
Botulism	Clostridium botulinum	Trivalent horse antitoxin (A, B, E) Heptavalent botulinum antitoxin

DESCRIPTION	S/X
From prolonged contact with droplets -> nerve injury and demyelination   Common in palawan	PAINLESS skin patch with loss of sensation Foot drop, clawed hands Ulcerations (leonine facies / lion-like)

CONDITION	CAUSATIVE AGENT	TREATMENT
Leprosy	Mycobacterium leprae

types of tetanus

Cephalic	following head injury or middle ear infection which cause dysfunction of the cranial nerves
Neonatal	contaminated material due to dress umbilical cord

types of botulism

Food botulism	Ingestion; acute GI sx from low acid veg, fruits, meals, fish, dairy, canned foods
Wound botulism	chronic iv drug abuse	Penicillin G
Infant botulism	ingestion of raw honey causing weak sucking response (floppy baby syndrome)

types of leprosy and their treatment

Paucibacillary leprosy	5 or fewer lesions; absence of organism	Dapsone; Rifampicin
Multibacillary leprosy	6 or more lesions; visualization of bacilli on smear	Dapsone/Rifampicin + Clofazimine

classification of leprosy

Tuberculoid (neural) form	w/ active immune response, CD4 abundant, benign; Lost of sensation
Lepromatous (progressive) form	w/ weak immune response, CD4 lacking, malignant; disfigured skin (lepromas)

exotoxin released by Clostridium tetani

tetanospamin