CNS Infections (Meningitis & Encephalitis) & Head Injuries CA

Question 1

What are the different types of infections of the CNS?

Answer 1

1. Bacteria
   e.g. meningitis
2. Viral
   e.g. encephalitis
3. Protozoa
   e.g. amoebic acscess
4. Helminthic infections

Question 2

What is meningitis and what are its causes?

Answer 2

• Inflammation of meninges surrounding brain & spinal cord , result in irritation of nerves that pass thru meninges

Causes: Bacteria/viruses/fungus

Question 3

Symptoms of meningitis

Answer 3

• Fever
• Headache
• Irritability
• Delirium
• LOC in severe cases
• Vomiting
• Joint pain
• Fitting
• Stiff neck
• Drowsiness

Question 4

Clinical signs of meningitis

Answer 4

(which indicate presence of nerve irritation)

1. Neck stiffness - pt feel pain, unable to touch their chin to their chest (sternum).
2. KERNIG’s SIGN - try to extend flexed knee when hip is flexed - cause spasm of hamstring muscles
   (KNEE EXTENSION IS PAINFUL)
3. BRUDZINSKI SIGN - Severe neck stiffness ; cause pt hips & knees to flex when neck is flexed
   (NECK FLEXION LEADS TO KNEE FLEXION)
4. Purpura (meningococcal meningitis)

Question 5

What investigations are done in a suspected case of meningitis?

Answer 5

1. CT scan to exclude mass lesion in drowsy or unconscious patients
2. Lumbar puncture
3. Blood culture (TRO septicemia)

Question 6

What would you expect the CSF of a positive meningitis case to contain?

Answer 6

1. Elevated WBC count, (neutrophils>5000: for bacterial meningitis)
   (lymphocytes: viral and tuberculous meningitis)
2. Elevated protein (due to inflammation and breakdown of BBB)
3. Glucose reduced
   (especially bacterial meningitis)
4. Gram stain may show organism (the causative bacteria)

Question 7

Treatment of meningitis

Answer 7

1. IV antibiotics
   (depending on infecting organism)
2. Supportive measures
3. Contacts of meningococcal meningitis require rifampicin prophylaxis
4. Vaccination

Question 8

Complications of meningitis

Answer 8

1. Cranial nerve palsies
   - due to fibrosis
2. Hydrocephalus
   - due to blockage of aqueduct
3. Cortical atrophy
   - due to vessel thrombosis, increases ICP
   - mental retardation, blindness, deafness, paralysis

Question 9

What is encephalitis?

Answer 9

Inflammation of PARENCHYMA of brain by viruses
e.g. Herpes simplex, VZ, CMV, JE

Produces symptoms of focal dysfunction

Inflammation can occur in cortex, white matter, basal ganglia, brain stem

Pathology - edema, haemorrhage, necrosis of temporal lobes

Question 10

Symptoms of herpes simplex encephalitis

Answer 10

• Behavioural & personality changes
• Focal neurological signs
  e.g. aphasia, hemiplegia
• Seizures
• Drowsiness and coma (extreme cases)

Question 11

Signs of herpes simplex encephalitis

Answer 11

1. Neck stiffness
2. Photophobia (cannot tolerate light)
3. Headache

Question 12

What is Japanese encephalitis?

Answer 12

Leading cause of viral encephalitis in Asia

Caused by the culex mosquito

Poeple in rural areas at risk, including expats working in rural areas

Vaccine is available

Question 13

Investigations for encephalitis

Answer 13

1. CT scan
   - exclude mass lesion
   - localise site of lesion (e.g. temporal lobes in herpes simplex encep)
2. LP
   - detect increased lymphocytes, elevated protein, normal glucose
3. EEG
   - slow waves in temporal lobes in herpes simplex encep

Question 14

Treatment of encephalitis

Answer 14

1. Anticonvulsants
2. Meds for raised ICP
   - dexamethasone
   - mannitol
3. Antivirals
   - IC acyclovir for herpes simplex encephalitis

usually poor prognosis
(residual epilepsy or cognitive impairment)

Question 15

What is a brain abscess encephalitis

Answer 15

encephalitis caused by localised collection of pus within brain PARENCHYMA

presents as space-occupying lesion

treatment: drainage/ or excision of abscess with IV antibiotic therapy

Question 16

When is a lumbar puncture performed in CNS infections/neuro disorders?

Answer 16

1. Used to diagnose CNS infections (e.g. meningitis)
2. Used to rule out SAH (“Thunderclap headache” when CT/MRI is normal or beyond 3 days)
3. Therapeutic function: to evaluate for normal pressure hydrocephalus with walk test

Question 17

What are the contra-indications to LPs?

Answer 17

1. Presence of infection in tissues near to puncture site
2. Presence of space occupying lesion
3. Bleeding tendencies

Question 18

What is the normal opening pressure in a LP? What does an elevated/low pressure indicate?

Answer 18

Normal: 10-18cm H20

Elevated:
- Infective: TB/bacterial/fungal
- Hydrocephalus (communicative type)
- Benign intracranial hypertension

Low:
- Blockage (spinal block but ICP is high)
- Intracranial hypotension

Question 19

What are primary and secondary brain injuries?

Answer 19

Primary brain injury is the initial impact and damage to the brain that occurs at the time of trauma.

Secondary brain injury involves delayed processes (like swelling or lack of oxygen) that worsen the damage and can be managed if treated quickly.

Question 20

Types of head injuries

Answer 20

Intracranial lesions: abnormal areas of tissue or masses located within the skull

• Concussion
• Contusion
• Extradural hematoma
• Subdural hematoma (acute/chronic)
• Subarachnoid hemorrhage
• Intracerebral hemorrhage

Question 21

What is a concussion

Answer 21

caused by a blow, bump, or jolt to the head or body, leading to the brain moving rapidly back and forth inside the skull—-rotation of cerebral hemispheres on the relatively fixed brainstem

no visible injury to the brain tissue on imaging (like CT or MRI scans)—– no structural lesion

Results in electro-physiological dysfunction of the reticular activating system

Question 22

Clinical features of a concussion

Answer 22

Characterised by immediate, transient LOC (dazed, “star-struck”)

1. Amnesia may occur after injury
2. Retrograde amnesia (memory loss for events before the injury)
3. Antegrade amnesia
   (past memories intact, unable to form new memories after the onset of the condition)

Question 23

What is a contusion

Answer 23

localized injury where small blood vessels are damaged, leading to bleeding (hemorrhage) into brain tissue

result in structural damage to brain tissue, usually visible on imaging (such as a CT scan), usually caused by more severe trauma

cause: deceleration of the brain against the skull rupturing the blood vessels on the surfaces of the brain
frontal and occipital poles affected

Question 24

Clinical features of a contusion

Answer 24

1. hemiparesis (one-sided weakness) or gaze paralysis may occur with frontal injuries (responsible for functions such as decision-making, personality, and voluntary movement)
2. visual defect in occipital injuries (responsible for vision)
3. cranial nerve dysfunction, commonly olfactory
4. more severe injury causes cerebral edema, decorticate or decerebrate rigidity
5. If cerebral lesions are bilateral—coma

Question 25

What is an extradural/epidural hematoma?

Answer 25

ARTERIAL BLEED: rapid worsening of patient's condition bleeding in between skull & dura mater (outermost brain protective lining) due to direct trauma causing fracture of the temporal bone and damage to middle meningeal artery Usually seen in head trauma among younger patients

Question 26

Clinical features of extradural/epidural hematomas

Answer 26

- brief LOC (due to concussion) followed by a short “lucid interval” (as brain hasn’t yet been significantly compressed by the expanding hematoma) then coma again (progressive neurological deterioration due to herniation) - bad prognosis - usually require surgical evacuation - untreated: decerebrate rigidity, coma, death

Question 27

How do epidural/extra hematomas look like on CT scans?

Answer 27

Convex, lens shaped

Question 28

What is an acute subdural hematoma?

Answer 28

VENOUS BLEED bleeding between dura mater and arachnoid membrane (middle layer, between dura and pia mater) may not be associated with any surface injuries on the scalp follows severe head injury - change in velocity due to rupture of the bridging cranial veins twice as common as extradural hematoma more commonly seen in trauma/falls among older people

Question 29

Clinical features of an acute subdural hematoma

Answer 29

- brief LOC (due to concussion) → RELATIVELY LONGER “lucid interval” → coma again (progressive neurological deterioration due to herniation - bad prognosis - usually required surgical evacuation - untreated: decerebrate rigidity, coma, death

Question 30

Why do acute SUBdural hematomas have a longer lucid interval than EXTRAdural/EPIdural hematomas?

Answer 30

Subdural hematoma: VENOUS bleed - often associated with skull fractures (especially of the temporal bone) that tear the middle meningeal artery - more rapid accumulation of blood, ICP rises more rapidly Extradural/epidural: ARTERIAL bleed - often caused by the tearing of bridging veins - bleeding is slower and more gradual, leading to a more prolonged time before significant symptoms appear - more gradual increase in ICP

Question 31

What are chronic subdural hematomas?

Answer 31

- follows minor injuries which may not be remembered - due to shrinking of the brain coupled with fragility of blood vessels common in >60yo

Question 32

Clinical features of chronic subdural hematomas

Answer 32

- sign & symptoms appear months to years after trivial injury - due to slow accumulation of venous blood around atrophied brain - symptoms may be absent, non-specific, non-localising commonly experience minor headaches over a period of time because of slow bleeding other symptoms: personality changes, fluctuating drowsiness, confusion, weakness, seizures - can be confused with stroke, dementia - potentially treatable

Question 33

What is subarachnoid hemorrhage and its clinical features?

Answer 33

bleeding into the subarachnoid space (between arachnoid and pia mater) often results from the rupture of an aneurysm/vascular malformation in the brain/head traumas clinical features: - "thunderclap" headache - N&V due to increased ICP - altered consciousness - neuro deficits - photophobia - stiff neck - seizures

Question 34

What is intracerebral hemorrhage and its clinical features?

Answer 34

bleeding that occurs within the brain tissue itself can be caused by various factors, including hypertension, vascular malformations, trauma, or bleeding disorders a sudden and severe headache, which can be localized or diffuse Sudden Onset of Symptoms Headache Neurological Deficits Altered Consciousness Nausea and Vomiting Seizures Abnormal pupillary response Increased Blood Pressure Stiff Neck

Question 35

Management of head injuries

Answer 35

ICP Management via: 1. BP management - maintain usual BP, keep MAP at 90 mmHg - too low BP: inadequate CPP - maintain CPP between 50-70 2. Hypocarbia - a state of reduced CO₂ levels in the blood, achieved through hyperventilation - when CO₂ levels drop (hypocarbia), the cerebral blood vessels constrict (vasoconstriction), leading to a reduction in cerebral blood flow, temporarily reduces ICP - used to acutely lower ICP when there are signs of brain herniation 3. Infusion of osmotic diuretics - Mannitol, glycerol IV - work by drawing water out of brain cells and into the bloodstream, which helps to reduce brain swelling (cerebral edema) and lower ICP - Caution: Water depletion and hypernatremia, requires frequent monitoring of electrolytes!

Question 36

Signs of a basal skull fracture

Answer 36

Soft tissue injuries: 1. Battle's sign: Bruising behind the ear (over the mastoid process), often indicating a fracture of the temporal bone---Postauricular ecchymoses 2. Raccoon's eyes: Bruising around both eyes, indicative of a fracture near the orbits (eye sockets)-----Periorbital ecchymoses 3. Hemotympanum: Blood in middle ear (behind the eardrum), suggests fracture of the temporal bone 4. CSF rhinorrhea (nose) & otorrhea (ear) due to a tear in the meninges Others: Cranial Nerve injuries anosmia, partial loss of vision, facial palsy, vertigo, nystagmus Note: 2/3 of patients with skull fracture are associated with intracranial lesions

Question 37

What constitutes the brain stem?

Answer 37

midbrain, pons, and medulla oblongata responsible for many vital functions of life, such as breathing, consciousness, blood pressure, heart rate, and sleep

Question 38

What are some signs of a brain stem lesion?

Answer 38

Altered consciousness, cranial nerve palsies, hemiparesis, respiratory issues, abnormal posturing 1. absence of occulovestibular reflex reflex that acts to stabilize gaze during head movement 2. Negative doll's eye reflex positive: eyes move in opposite direction of head movement 3. Absent corneal reflex: Loss of sensation in the eye or inability to blink when touched 4. Abnormal pupillary light reflex

Question 39

What are some signs of a cerebellum lesion?

Answer 39

cerebellum: coordinates body movement Ataxia (loss of muscle control), dysmetria (lack of coordination), intention tremor, dysdiadochokinesia (inability to perform rapid alternating muscle movements), nystagmus, vertigo, dysarthria Finger-to-nose test, heel-to-shin test, Romberg test (measures sense of balance), rapid alternating movements (RAM).

Question 40

What are some signs of a frontal lobe lesion?

Answer 40

frontal lobe: manage thinking, emotions, personality, judgment, self-control, muscle control and movements, memory storage and more Motor weakness, behavior changes, Broca’s aphasia (loss of language), impaired executive function Grip strength, plantar reflex (Babinski sign), return of primitive reflexes.