General Neuro Flashcards
What is decorticate posturing and what does it represent?
Flexed upper limbs and extended lower limbs, spontaneous or on stimulus
Indicates an insult to the hemispheres, internal capsule and/or thalamus
Mnemonic is you “Catch a ball” with Decorti”cat(ch)”e
M3 for GCS
What is decerebrate posturing and what does it represent?
Extended upper limbs and extended lower limbs
Indicates brain stem pathology, progressive to decerebrate posturing may represent brainstem herniation
M2 for GCS
What are the causes of fixed dilated pupils?
Brain death
Significant mass effect leading to bilateral 3rd nerve compression
Generalised seizures
Severe hypothermia
Barbituates
Severe hypoxia
Anticholinergics/Adrenaline
High intrinsic catecholamine release
What are the causes of a unilateral fixed dilated pupil
Significant mass effect/tentorial herniation (3rd nerve compression)
Focal seizures
Direct eye injury
3rd nerve palsies
What are the causes of bilateral pinpoint pupils
Opiates
Organophosphate poisoning
Medullary lesions
Metabolic disorders
What is the utility of the different IV therapies for Meningitis?
Dexamethasone- reduces ICP and proven to reduce rates of deafness
Ceftriaxone- Targets main organisms of strep, meningococcus, HiB
Benzylpenicillin- Targets Strep and Listeria
Vancomycin- Targets Beta lactam resistant organisms ie MRSA or resistant strep
What is Xanthochromia?
The yellowish discolouration of the CSF due to breakdown of haemoglobin from blood into bilirubin and oxyhaemoglobin in the CSF
Xanthochromia can also occur with systemic hyperbilirubinaemia and very high CSF protein levels
When is Xanthochromia detectable and how long does it last?
Detectable as early as 2-4hrs post bleeding, although 90% of people will have this within 24hrs
Can last 2-4 weeks
What are the classic LP findings in SAH?
Elevated opening pressure
Xanthochromia
Elevated RBC count that doesnt change from tubes 1-4
- this is poorly sensitive and specific
- <2000RBCs/uL + no xanthochromia is 100% sensitive for no SAH
What are the findings in CSF with bacterial meningitis?
Low glucose (strongly sensitive but not specific)
Oligoclonal bands
Raised WCC’s with PMN predominance
Raised protein levels
Gram stain +ve
Culture +ve
What is autonomic dysreflexia?
Occurs in people with spinal cord injuries above T6
Uninhibited or exaggerated response to noxious stimuli below the level of the spinal cord lesion ie severe hypertension and tachycardia
Why does autonomic dysreflexia generally not occur below T6?
Intact splanchnic innervation allows for compensatory splanchnic bed dilatation
How is autonomic dysreflexia treated?
- Sit the patient upright to lower the BP orthostatically
- Remove any tight fitting clothing
- Treat underlying cause (constipation and bladder distension most common)
- BP lowering agents ie GTN, hydralazine and labetalol with caution
- Prevention with meds such as nifedipine and prazosin
What are the differentials for unilateral weakness/neurological symptoms (ie stroke mimics)?
Ischaemic stroke
haemorrhagic stroke/ICH
Migraine
Todds paresis
Hypoglycaemia
Functional
MS
Brain tumour
Brain abscess
Bells Palsy
Hyponatraemia
Encephalopathy (hypertensive, hyper ammonaemic etc)
RCVS
What are the stats around meningitis?
- 90% of cases occur in 1st 5yrs
- MO’s usually enter via haematogenous spread
- Mortality/Morbidity still high despite antibiotics
- Occrs in 20-100:100,000 neonates
What are the main causes of Aseptic meningitis?
Viral
- Mumps, EBV, echo, HSV, cocksackie and HIV
Bacterial
- Mycoplasma, Borrelia, syphilis, Brucella
Fungi/Parasite
- Toxoplasma, cysticercosis
Other
- Sarcoid, SLE, Wegners, NSAID’s
What does a low glucose in CSF potentially indicate?
Normal CSF glucose is 60-80% of the serum glucose
Decrease usually indicates diffuse meningeal inflammation
Viral meningitis has normal glucose except Mumps and occasionally HSV and HZV which make it low
How should CSF results be interpreted in bacterial meningitis?
- Gram stain variably sensitive, 30-90% for meningococcus, 70-90% for pneumococcus
- CSF WCC more than 100 is 99% sens
- > 80% Neuts is highly specific
- TB meningitis will be gram stain negative and have a lymphocyte predominance
How does interpretation change when a patient is pre-treated with antibiotics?
- CSF becomes sterile approx 2-10hrs post IV ABx
- > 12hrs biochemistry is altered as well with higher glucose and lower protein levels than typical for meningitis
When and how should dexamethasone be used in meningitis?
- Most effective in the pneumococcal meningitis
- Reduces cytokine mediated complications
- the dose in adults is 10mg IV QID and 0.15mg/kg IV in children
- Dexamethasone has not been shown to be effective in neonates and is not recommended
- In Children it has been shown to reduce neurological and audiological complications
What are the main Guillane-Barre variants?
Acute Inflammatory Demyelinating Polyradiculoneuropathy (AIDP)
- This is the most common (90%) and the classical GBS variant
- Acute bilateral ascending paralysis starting distally
- 85% have sensory changes
- 1/3rd get severe pain, typically back pain
Acute Motor Axonal Neuropathy
- Motor only variant of AIDP, the 2nd most common variant
Pharyngeal-Cervical-Brachial
- Bulbar dysfunction, neck and shoulder weakness but upper and lower limbs spared
Polyneuritis Cranialis
- Acute bilateral multiple cranial nerve dysfunction + peripheral sensory loss
- younger + cytomegalovirus infection
Bickerstaff Encephalitis
- Brainstem inflammation with hyper reflexia, encephalopathy, ataxia and ophthalmoplegia
Acute Pandysautonomia
- Usually occurs in children
- BP swings, dysrhythmias, bladder issues, inappropriate sweating and paralytic ileum
- altered reflexes and sensation
Miller-Fisher Syndrome
- Triad of Ophthalmoplegia, ataxia and areflexia
What is Bells Palsy? What are the risk factors and possible causes? what is the treatment?
Idiopathic isolated 7th nerve palsy
Symptoms/Signs
- Ipsilateral upper/lower facial weakness
- Ipsilateral reduced taste/salivation (Chorda tympani branch)
- Ipsilateral reduced eye tearing (petrosal branch)
- ipsilateral hyperacusis (nerve to stapedius)
RF’s
- Pregnancy, hypertension
Causes
- Idiopathic
- HSV + other viruses
- Lyme disease
- Leukaemia
- Ischaemic
- Diabetes
- Autoimmune (GBS, MS, sarcoidosis, temporal arteritis)
- Post vaccination
- Trauma
- brain tumour
MX
- PO Prednisolone 1mg/kg max 75mg for 5 days
- PO Valaciclovir 100mg TDS 7 days
- Ocular: HB score 4-6, consider nightly eye tape, ngihtly parafin ointment and PRN lubricants
- Dental: usually 4-6, for those unable to close mouth, significant oral dryness increases risk of caries
What are the features differentiating Bells palsy from more sinister causes?
What is the prognosis?
- Worsens in 1st 3 weeks then start to recover (85%)
- 71% will recover in 12 months
- 94% have complete recovery
- Higher HB scores portend risk of incomplete recovery
- May have abberant neurology on recovery (Crocodile tears etc)
Neuro referral if
- Atypical or severe symptoms
- No recovery within 4 weeks
- Incomplete recovery within 3 months
What are the differences on clinical examination between peripheral and central vertigo?
How is the HINT’s exam used with vertigo?
Nystagmus must be present at rest to use the HINT’s exam
What are the causes of low glucose in CSF (Hypoglycorrhachia)?
- Severe hypoglycaemia can cause it, although technical definition is CSF/serum ratio <0.6 (normal is approx 0.6 or greater)
- Ie hypoglycorrhacia is a relative, no absolute lack of glucose in the CSF relative to the serum
- salicylate toxicity is a rare cause
What are the different medications that can be used for migraines and their pros/cons?
