29. DMD CNS 2025

cons q

what is viral meningitis cause by - Mumps, enterovirus

wht is encephalitis caused by - herps reactivation

wht is brain abscess caused by - streptococal, anaerobes

waht is facial palsies caused by - VZV - reactivation

transissable spongiform encephalopathies - prions

waht is CJD a type of - transmissible spongiform encephalopathies

wt causes conjunctivitis, HSV, clamydia trachomatis, Adenovirus

wt causes karetinits -HSV, Clamydia trachomatis

wt causes retinitis - CMV - esp inAIDs

Learning Aims

• Ability to outline key aspects of:

  • Acute Meningitis: Clinical appearance, epidemiology, etiology, treatment approaches.

  • Brain Abscesses & Encephalitis: Aetiology, clinical presentation, treatment approaches.

  • Creutzfeldt-Jakob Disease (CJD): Classification, pathogenesis, routes of transmission, epidemiology.

  • Key Eye Infections: Conjunctivitis, keratitis, retinitis.

Pathways for CNS Infection

• Mechanisms for organism entry into the CNS include:

  • Contiguous Spread: Infection from sinuses, ear, mastoid, or face.

  • Trauma: Direct inoculation from injuries.

  • Hematogenous Spread: Via the bloodstream

  • via nerves.

Inflammation of CNS Structures

• Meningitis: Inflammation of the meninges.

• Encephalitis: Inflammation of the brain substance.

Symptoms of Meningitis

• Common symptoms include:

  • Fever & Stiff Neck

  • Photophobia

  • Headache

  • Vomiting

  • Irritability & Drowsiness

Types of Meningitis

• Viral Meningitis:

  • More common, often benign, usually leads to complete recovery.

• Common viruses: Enteroviruses, Mumps virus.

• Bacterial Meningitis:

  • Less common but more severe, can lead to mortality and morbidity.

  • Common bacteria:

    • Neisseria meningitidis

    • Streptococcus pneumoniae

    • Haemophilus influenzae.

Examination Findings in Meningitis

• Bacterial vs. Viral:

  • Presence of neutrophils, glucose levels, protein concentrations, and culture results vary.

  • large decrease in glucose and large increase in protein in bacterial meningitis

• Increased neutrophils suggest bacterial; lymphocytes indicate viral causes.

Bacterial Meningitis as a Medical Emergency

• Focus on the big three: NHS - medical emergency

  • Neisseria meningitidis

  • Haemophilus influenzae (specifically capsule type b)

  • Streptococcus pneumonia

Neisseria meningitidis (Meningococcus)

• Most common and severe form, particularly in children (<5) and young adults (15-20).

• Characterized by:

  • Meningococcal Meningitis with a rash, purpura, non blanching on tumbler test

  • clusters - It's carried in the nose/throat of some people without symptoms, and can spread via coughing, sneezing, or kissing.

  • Various capsule types with vaccines available for types A, C, and B.

  • case b more popular in uk

  • transmittion via respiratory droplets, more common in winter

• The virus hat cause bacterial meningitis can also cause septicaemia. Septicaemia can occur with or without meningitis. 

Control & Prevention for Meningococcal Disease

• Public health responses to clusters include:

  • Antibiotic prophylaxis.

  • Vaccination strategies targeting types A and C, with newer types for B.

Vaccination Against Meningitis

• Tetravalent Vaccine: Covers serotypes A, C, Y, & W135. but not B

• Men C conjugate vaccine included in UK childhood immunization schedule.

• Men B vaccine more common in uk

Pneumococcal meningitis SP

• Caused by Streptococcus pneumoniae, often seen in older populations or post-head trauma.

• Resistance to penicillin is a growing problem

• prevention - vaccines

Haemophilus Meningitis HI

• Mainly from Haemophilus influenzae type b; children 1-5,

• significantly reduced incidence after the introduction of HIB vaccine.

• prevention - HIB vaccine and Antibiotic prophylaxis for close contacts important for management.

Tuberculosis Meningitis

• Caused by Mycobacterium tuberculosis.

• Prolonged treatment with anti-TB medications is required; infection usually originates from lungs.

Viral Meningitis

• The most common type of meningitis; typically benign with complete recovery.

• CSF- shows no bacteria but with Enterovirus (Coxsackie, Echovirus), VZV, and Mumps.

• PCR to identify virus

• no specific treatment

Diagnosis of Meningitis

• Lumbar puncture (LP) checks for:

  • Intracranial pressure

  • CSF examination: WBC cell counts, glucose and protein chemistry, staining films, cultures, PCR.

Management of Bacterial Meningitis

no specfic treatment for viral

• Urgent Management:

  • Immediate antibiotic therapy; administer benzyl penicillin for suspected meningococcal disease.

  • cefotaxime or ceftriaxone for unknown bacterial causes.

Encephalitis Overview

• Inflammation of brain substance; primarily caused by the herpes simplex virus (HSV-1) in temporal lobe brain as a reactivation infection

• Symptoms include stroke-like signs, memory loss, behavioral changes, seizures.

• Aciclovir for treatment

Other Causes of Encephalitis

• Enteroviruses (summer-autumn occurrences).

• Arboviruses (mosquito-borne, e.g., West Nile).

• Rabies: 100% fatal without intervention; spread from animal bites.

Brain Abscess

• Caused by bacteria - streptococi, anaeobes

• Focal (specifc) infection characterized by a collection of pus, often related to: otitis media, sinusitis, dental abscess, or trauma, endocarditis

• Symptoms similar to encephalitis

• management typically requires surgical intervention along with antibiotics.

Cranial Nerve Palsies

• Cranial nerve palsies occur when one or more of the 12 cranial nerves, which connect the brain to the head, face, and neck, malfunction, causing a range of symptoms like double vision, droopy eyelids, or facial weakness. 

• facial (7) nerve plasies - VZV reactivation (Ramsay Hunt Syndrome).

• symptoms - facial paralysis and shingles rash

Introduction to Prions

• misfold proteins causing normal proteins in the brain to misfold as well

• Unconventional 超脫 infectious agents, tiny, lacking nucleic acid;

• resistant to heat, disinfection, UV radiation, sterilization techniques.

• Long incubation periods with no immune response observed.

Transmissible Spongiform Encephalopathies (TSEs)

• Includes Creutzfeldt-Jakob Disease (CJD); may be genetic, sporadic零落, or infectious.

• Transmission by abnormal folding of prion proteins (PrP).

• abormal prions inducing other normal proteins in the brain to misfold, leading to progressive brain damage.

• due to its sporadic characteristic, genetic mutation in PrP, infectious person to person

CJD Creutzfeldt-Jakob Disease and Variant CJD (vCJD)

• caused by abnormal folding of prions, lead to brain degeneration → dementia, memory loss

• Sporadic/spontaneous CJD (sCJD) – ~85% of cases

  • Happens randomly, without known cause

• Hereditary CJD – ~10–15%

  • Mutation in the PRNP gene

• Acquired CJD – very rare

  • Includes:

    • Variant CJD (vCJD) – linked to mad cow disease (bovine spongiform encephalopathy)

    • Iatrogenic CJD – via medical procedures (e.g., contaminated instruments)

prion transmission ways

✅ 1. CNS Tissue (Central Nervous System)

• Instruments used on the brain/spinal cord can carry prions.

• Neurosurgical tools and brain electrodes have caused transmission.

• Prions are very sticky — they stick to metal and resist sterilization.

✅ 2. Tonsils in Variant CJD (vCJD)

• In variant CJD (linked to mad cow disease), prions can be found in lymphoid tissue, including tonsils.

• This means even a tonsillectomy could pose a transmission risk.

✅ 3. Blood Transfusions

• There have been documented cases of vCJD being spread through blood transfusion.

• This is why donor screening is so strict in some countries (e.g., UK restrictions on donating if you lived there in the 1980s–90s).

✅ 4. Human Growth Hormone

• In the past, growth hormone was taken from cadaver brains, which spread prions to children.

• This is no longer done — now it's made synthetically.

⚠ Concerns/Worries (Less Proven, But Possible):

❓ 5. Nerve Tissue in General

• Prions are highly concentrated in nervous tissue.

• So even tissues with nerves — like gingival tissue (gums) or dental pulp (inside teeth) — are considered potentially risky.

• There’s concern about dental procedures like root canals.

❓ 6. Dental Instruments (like Endodontic Files)

• Files used in root canals may come into contact with nerve tissue.

• Because prions are resistant to standard sterilization, there’s concern that they could stay on instruments and infect another patient.

😵‍💫 Why is this confusing?

• Hard to quantify risk → It's rare, and we can't easily test for prions.

• Many concerns are precautionary rather than based on frequent real-world cases.

• But because prion diseases are fatal and untreatable, even small risks are taken very seriously.

Eye Infections

• Focus on conjunctivitis, keratitis, retinitis.

Conjunctivitis

• Infectious agents include:

  • Bacteria and adenovirus; highly infectious and usually bilateral.

  • HSV can lead to karatitis

  • Chlamydia trachomatis (STI) through auto-inoculation, often maternal transmission.

Keratitis

• Infection of the cornea

• HSV repeated reactivation leading to scarring

• Chlamydia trachomatis (bacteria) associated with trachoma. (eye disease)

Retinitis

• Commonly associated with CMV, especially in AIDS patients.

• Toxoplasmosis in utero related to maternal infections from cat feces or undercooked meat,

• presenting with visual disturbances.