CNS Infections (Meningitis & Encephalitis) & Head Injuries CA Flashcards
What are the different types of infections of the CNS?
- Bacteria
e.g. meningitis - Viral
e.g. encephalitis - Protozoa
e.g. amoebic acscess - Helminthic infections
What is meningitis and what are its causes?
- Inflammation of meninges surrounding brain & spinal cord , result in irritation of nerves that pass thru meninges
Causes: Bacteria/viruses/fungus
Symptoms of meningitis
- Fever
- Headache
- Irritability
- Delirium
- LOC in severe cases
- Vomiting
- Joint pain
- Fitting
- Stiff neck
- Drowsiness
Clinical signs of meningitis
(which indicate presence of nerve irritation)
- Neck stiffness - pt feel pain, unable to touch their chin to their chest (sternum).
- KERNIG’s SIGN - try to extend flexed knee when hip is flexed - cause spasm of hamstring muscles
(KNEE EXTENSION IS PAINFUL) - BRUDZINSKI SIGN - Severe neck stiffness ; cause pt hips & knees to flex when neck is flexed
(NECK FLEXION LEADS TO KNEE FLEXION) - Purpura (meningococcal meningitis)
What investigations are done in a suspected case of meningitis?
- CT scan to exclude mass lesion in drowsy or unconscious patients
- Lumbar puncture
- Blood culture (TRO septicemia)
What would you expect the CSF of a positive meningitis case to contain?
- Elevated WBC count, (neutrophils>5000: for bacterial meningitis)
(lymphocytes: viral and tuberculous meningitis) - Elevated protein (due to inflammation and breakdown of BBB)
- Glucose reduced
(especially bacterial meningitis) - Gram stain may show organism (the causative bacteria)
Treatment of meningitis
- IV antibiotics
(depending on infecting organism) - Supportive measures
- Contacts of meningococcal meningitis require rifampicin prophylaxis
- Vaccination
Complications of meningitis
- Cranial nerve palsies
- due to fibrosis - Hydrocephalus
- due to blockage of aqueduct - Cortical atrophy
- due to vessel thrombosis, increases ICP
- mental retardation, blindness, deafness, paralysis
What is encephalitis?
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
Symptoms of herpes simplex encephalitis
- Behavioural & personality changes
- Focal neurological signs
e.g. aphasia, hemiplegia - Seizures
- Drowsiness and coma (extreme cases)
Signs of herpes simplex encephalitis
- Neck stiffness
- Photophobia (cannot tolerate light)
- Headache
What is Japanese encephalitis?
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
Investigations for encephalitis
- CT scan
- exclude mass lesion
- localise site of lesion (e.g. temporal lobes in herpes simplex encep) - LP
- detect increased lymphocytes, elevated protein, normal glucose - EEG
- slow waves in temporal lobes in herpes simplex encep
Treatment of encephalitis
- Anticonvulsants
- Meds for raised ICP
- dexamethasone
- mannitol - Antivirals
- IC acyclovir for herpes simplex encephalitis
usually poor prognosis
(residual epilepsy or cognitive impairment)
What is a brain abscess encephalitis
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
When is a lumbar puncture performed in CNS infections/neuro disorders?
- Used to diagnose CNS infections (e.g. meningitis)
- Used to rule out SAH (“Thunderclap headache” when CT/MRI is normal or beyond 3 days)
- Therapeutic function: to evaluate for normal pressure hydrocephalus with walk test
What are the contra-indications to LPs?
- Presence of infection in tissues near to puncture site
- Presence of space occupying lesion
- Bleeding tendencies
What is the normal opening pressure in a LP? What does an elevated/low pressure indicate?
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
What are primary and secondary brain injuries?
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.
Types of head injuries
Intracranial lesions: abnormal areas of tissue or masses located within the skull
- Concussion
- Contusion
- Extradural hematoma
- Subdural hematoma (acute/chronic)
- Subarachnoid hemorrhage
- Intracerebral hemorrhage
What is a concussion
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
Clinical features of a concussion
Characterised by immediate, transient LOC (dazed, “star-struck”)
- Amnesia may occur after injury
- Retrograde amnesia (memory loss for events before the injury)
- Antegrade amnesia
(past memories intact, unable to form new memories after the onset of the condition)
What is a contusion
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
Clinical features of a contusion
- hemiparesis (one-sided weakness) or gaze paralysis may occur with frontal injuries (responsible for functions such as decision-making, personality, and voluntary movement)
- visual defect in occipital injuries (responsible for vision)
- cranial nerve dysfunction, commonly olfactory
- more severe injury causes cerebral edema, decorticate or decerebrate rigidity
- If cerebral lesions are bilateral—coma
What is an extradural/epidural hematoma?
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
Clinical features of extradural/epidural hematomas
- 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
How do epidural/extra hematomas look like on CT scans?
Convex, lens shaped
What is an acute subdural hematoma?
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
Clinical features of an acute subdural hematoma
- 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
Why do acute SUBdural hematomas have a longer lucid interval than EXTRAdural/EPIdural hematomas?
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
What are chronic subdural hematomas?
- follows minor injuries which may not be remembered
- due to shrinking of the brain coupled with fragility of blood vessels
common in >60yo
Clinical features of chronic subdural hematomas
- 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
What is subarachnoid hemorrhage and its clinical features?
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
What is intracerebral hemorrhage and its clinical features?
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
Management of head injuries
ICP Management via:
- BP management
- maintain usual BP, keep MAP at 90 mmHg
- too low BP: inadequate CPP
- maintain CPP between 50-70 - 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 - 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!
Signs of a basal skull fracture
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
- Raccoon’s eyes: Bruising around both eyes, indicative of a fracture near the orbits (eye sockets)—–Periorbital ecchymoses
- Hemotympanum: Blood in middle ear (behind the eardrum), suggests fracture of the temporal bone
- 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
What constitutes the brain stem?
midbrain, pons, and medulla oblongata
responsible for many vital functions of life, such as breathing, consciousness, blood pressure, heart rate, and sleep
What are some signs of a brain stem lesion?
Altered consciousness, cranial nerve palsies, hemiparesis, respiratory issues, abnormal posturing
- absence of occulovestibular reflex
reflex that acts to stabilize gaze during head movement - Negative doll’s eye reflex
positive: eyes move in opposite direction of head movement - Absent corneal reflex: Loss of sensation in the eye or inability to blink when touched
- Abnormal pupillary light reflex
What are some signs of a cerebellum lesion?
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).
What are some signs of a frontal lobe lesion?
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.
