Neuro Flashcards
What 3 bugs are most commonly implicated in community acquired bacterial meningitis?
- Step pneumoniae
- Neisseria meningitidis
- Haemophilus influenzae
What is the pathogenesis of acute bacterial meningitis?
- Nasopharyngeal colonisation occurs.
- Blood stream invasion occurs across the mucosa
3 Circulation of bacteria to the CNS via bloodstream
- In immunocompetent the bacteria is usually cleared by mucosal immunity. Co-infeciton with a resp virus increases inflammation.
-Occasionally it spreads directly through the olfactory bulb and therefore no bacteraemia is present (10-30%\0
When should dexamethasone be given in meningitis and why?
In suspected pneumococcal ABM with first antibiotics
- Decreases morbidity a.w CNS tissue damage e.g. deafness, CVA, epilepsy, LD
How does meningitis present?
Early - headache, leg pain, cold hands and feet, abnormal skin colour
Later - neck stiffness, photophobia, kernig +ve, reduced GCS, seizures, opishotonus, petechial rash, sepsis
What are the CI to LP in suspected ABM?
If suspected mass lesion, focal signs, papilloedema, trauma, middle ear pathology, coagulopathy
What is a normal CSF opening pressure?
7-18cm
What might the LP show in ABM?
- Raised opening pressure
- Turbid appearance
- Predominant cell type = polymorph
- Glucose = < 1/2 plasma
- Protein (g/L) > 1.5
- Cell count 90-1000+/mm3
- Bacteria on smear and culture
- Lactate > 3.5 predicts bacterial meningitis quite well
What are the LP findings in TB meningitis?
- Appearance = fibrin web
- Predominant cell type = mononuclear
- Cell count = 10-1000
- Glucose = < 1/2 plasma
- Protein = 1-5
- Bacteria - often none seen
What are the LP findings in someone with viral meningitis
- Appearance = clear
- Predominant cell type = mononuclear
- Cell count = 50-1000
- Glucose = > 1/2 plasma
- Protein = < 1
- Bacteria = none seen of culutres
What are the normal CSF values?
- < 5 lymphocytes may be normal as long as there are no neutrophils
- Protein 0.15-0.45 g/L
- Gluc 2.8-4.2
What causes reduced CSF glucose?
Sepsis
Parasitic meningitis e.g. from eating snails
Herpes encephalitis
Low blood glucose
Sarcoid
CNS vasculitis
What is Lance Adams syndrome?
A rare type of postanoxic myoclonus
Mainly action induced and occur when pt is awake
Prognosis is generally good
What is myoclonus?
Sudden, brief repetitive irregular and involuntary muscle jerks
Postanoxic myoclonus is usually seen in the face, trunk and limbs
Sometimes triggered by touching pt or clapping
If status myoclonus (continuous for >30mins) occurs within 48 hours = poor outcome predictor
How can seizures be differentiated from myoclonus?
Seizures are highly rhythmic and opposed to the irregular myoclonic jerks
With seizures there my be lateralisation e.g. turning of head and eyes
EEG can help differentiate
Seizures are rare post cardiac arrest, myoclonus is common
What is the blood supply to the brainstem?
Basilar artery
What are the 3 major parts of the brain stem?
Midbrain, medulla and pons
When should a brainstem syndrome be considered?
- sensory or motor deficits combined with CN palsy
- Impaired consciousness
- Dysautonomia
- Neurological resp failure
- Abnormal movements e.g. hemichorea, dystonia
- Swallow imapirment, dysphonia and emotional lability
What is locked-in syndrome?
Intact awareness, quadriplegia, anarthria and abscence of eye movementd excelt vertical gaze
Results from bilateral pontine white matter lesions
What is a vegetative state?
Unresponsiveness in which the patient shows spontaneous eye opening without any behavioural evidence of self or environmental awareness
What is a minimally conscious state?
Severely impaired consciousness with minimal behavioural evidence of self or evnironmental awareness, characterised by the presence of non-reflexive behaviour or even intermittently obeying commands
Why do PVS and MCS states occur?
Preservation of brain stem arousal functions with impairment of the supratentorial networks implicated in consciousness
What are the typical features of an anterior cerebral artery stroke?
Weakness of contralateral leg
Behaviour changes
What are the typical features of an MCA stroke?
-Weakness of contralateral face and arm
- Aphasia and dysarthria
- Hemianopia
- Inattention to stimuli
- Sensory deficit
What are the typical features of a vertebrobasilar stroke?
Dizziness
Ataxia
Impaired balance
Pupil and eye movement abnormalities
Changes in voice and swallowing
Weakness and sensory changes
Decreased consciousness
What are the typical features of a posterior cerebral artery stroke?
Visual field deficits
Sensory deficits
What are the typical features of cerebral vein and sinus thrombosis?
Decreased consciousness
Headache
Vomiting
How is stroke classified?
Bamford classification
What are the features of total anterior circulation syndrome (TACS)?
Part of Bamford classification of stroke.
All 3 of:
1. Unilateral motor, sensory deficit or both affecting at least 2 of face, arm or leg
2. Higher cerebral dysfunction e.g. dysphasia, dyspraxia
3. Homonymous hemianopia
-> due to occlusion of MCA
What are the features of partial anterior circulation syndrome (PACS)
Part of Bamford classification of stroke.
2 or 3 components of TACS
-> due to occlusion of MCA / branch of ACA
What are the features of lacuna syndrome (LACS)
Part of Bamford classification of stroke.
1. Pure motor or sensory deficit affecting at least 2 of face, arms, legs
2. Sensorimotor deficit not meeting TACS/PACS criteria
3. Ataxic hemiparesis
4. Dysarthria and clumsy hand
-> Due to occlusion of small, deep penetrating artery causing subcortical stroke
What are the features of posterior circulation syndrome (POCS)?
Part of Bamford classification of stroke.
1. Isolated homonymous hermianopia or cortical blindness
2. Brainstem or cerebellar syndromes / cranial nerve palsy
3. Loss of consciousness
-> circ issue with brainstem / cerebellum / occipital lobe
What imaging may be needed in suspected stroke?
- CT - rules out bleeding but an early scan may not demonstrate infarct. MRI is more superior for this
- Dopplers
- TTE - > should be considered in young is > 1 territory involved, murmur or abnormal ECG. Bubble ECHO if R->L shunt suspected.
What should thrombolysis be given for CVA?
Within 4.5 hours of symptom onset
How should BP be managed in acute phase of a stroke?
Uncertainty as hypertension is a compensatory mechanism to maintain perfusion.
- Treat is hypertensive emergency
- If no end-organ dysfunction then BP up to 220/120 may be tolerated
- If thrombolysis is an option then recommendation is BP < 185/110
What are the CIs to thrombolysis in CVA?
- Acute or pervious intracranial haemorrhage
- Severe uncontrolled hypertension (>185/110)
- Serious head trauma / CVA within 3 months
- Plts < 100
- INR > 1.7
- Current use of anticoagulants or treatment dose heparin within 48 hours
- Major surgery within last 14 days
- Recent GI/GU beeling within 3 weeks
- Severe hypo or hyperglycaemia
- Seizure at onset of stroke
- CNS structural lesion
- Isolated mild neuro deficits
- Recent MI
When should decompressive craniectomy be considered in CVA?
- < 60 years
- Clinical neurology in keeping with MCA infarct
- National institute of health stroke scale > 15
- CT demonstrating evidence of infarct of at least 50% of MCA territory
When does focal cerebral ischaemia result in coma?
- Brainstem stroke
- Malignant MCA syndrome
- Cerebral venous thrombosis
