Neuro Flashcards
Name the three most common scoring systems in the UK for grading the severity of SAH
World Federation of Neurological Surgeons (WFNS) (clinical)
Hunt & Hess (clinical)
Fisher grade (CT grading)
What are the causes of SAH?
Rupture of berry aneurysm
Rupture of AVM
Traumatic SAH
Name some risk factors for developing aneurysmal SAH
Smoking Polycystic kidneys Cocaine use Amphetamine use Ehler’s Danlos Genetic
Name some early neurological complications of SAH
Rebleeding
Seizure
Hydrocephalus
Name some later neurological complications of aneurysm SAH
Delayed cerebral ischaemia/vasospasm
Cognitive impairment
Neurocognitive symptoms - low mood/sleep disturbance
Hypopituitarism
List some indications for awake craniotomy
Epilepsy surgery
Tumour resection in eloquent areas of brain
DBS
List the absolute contraindications to awake craniotomy
Cannot lie still
List the relative contraindications to awake craniotomy
Learning difficulties Airway concerns - OSA Chronic cough Anxious patients Language barrier Children unable to cooperate
Name 3 anaesthetic approaches to awake craniotomy
- Asleep -> awake
- Asleep -> awake -> asleep
- Sedation - awake throughout
- No sedation/regional only (uncommon)
What intraoperative adverse incidents may occur in an awake craniotomy?
Airway problems & hypoventilation Conversion to GA required Seizure Air embolism Patient intolerance/revoking consent
Describe the flow of CSF in the brain
Choroid plexus in the LATERAL ventricles -> Foramen of Munro -> THIRD ventricle -> Sylvian aqueduct -> FOURTH ventricle -> Foramen of Magendie & Luschka -> spinal canal -> arachnoid villi ->dural venous sinuses
What are the clinical features of acromegaly?
OSA Coarsening facial features - macroglossia, prognathism, big ears Carpal tunnel syndrome Soft tissue changes - increased sweating, big hands Headache Hypertension T2DM Cardiomegaly/cardiomyopathy Vocal cord hypertrophy - deep voice
During trans-sphenoidal resection of pituitary tumour, the surgeon asks you to facilitate the descent of the pituitary into the operative field. How could you do this?
- Controlled hypercapnoea (decrease MV)
- Injection of saline into a lumbar drain
What follow up do patients need post pituitary resection?
IGF-1 levels
Colonoscopy
Visual fields
What are the endocrine complications of pituitary tumour resection?
Diabetes insipidus
Adrenocortical deficiency
Panhypopituitarism
What are the neurosurgical complications post pituitary adenoma resection?
CSF leak/rhinorrhea
Vascular injury - carotid artery
Optic nerve injury
Nasal septum perforation
Infection - meningitis/sinusitis
Anosmia
What is secondary brain injury and when is it likely to occur?
Deleterious changes that happen over hours/days as a consequence of the initial injury
Mediated by inflammatory, neurogenic and vasogenic processes
What is the pathophysiology of secondary brain injury?
- Reduced cerebral O2 delivery
- Increased CMRO2
- Cellular mechanisms
-Primary injury may exhaust compensatory capacity of brain (e.g. ICH) -> raising ICP & Monro Kelly Doctrine
-Inflammation/local tissue damage -> release of excitatory neurotransmitters causing calcium influx to cells and cell death
-Dying cells release free radicals causing increased blood vessel permeability and causing vasogenic fluid accumulation
-Loss of cerebral auto regulation
-Hypoxia/hypotension/hypercarbia/hypocarbia/hypoglycaemia/hyperglycaemia -> exacerbate secondary brain injury and inhibit auto-regulation
-Seizures cause raised ICP, raised CMRO2 and reduce PaO2
How can secondary brain injury be minimised?
ABCDE: Airway control -> I&V if low GCS/seizures/hypoxic/hypercarbia/unable to protect airway C spine control PaO2 >12 PaCO2 <4.5kPa PEEP for oxygenation but otherwise avoid Maintain MAP >80mmHg (or higher if ICP raised) Allow good venous drainage - head neutral, head up etc Catheterise Seizure control Temp control BM control Sedate to control CMRO2 ICP monitoring
What are the grades of severity with the WFNS for SAH?
- GCS 15, no motor deficit
- GCS 13-14, no motor deficit
- GCS 13-14 with motor deficit
- GCS 7-12 with or without motor deficit
- GCS 2-6 with or without motor deficit
What is autonomic dysreflexia?
Disorganised spinal sympathetic response to stimuli below the level of the lesion
Spinal circuits below the lesion are established and cause exaggerated responses
Sympathetic activation causes massive vasoconstriction and hypertension
Intact baroreceptors sense the hypertension causing reflex bradycardia
Descending inhibitory pathways not transmitted due to discontinuous cord
What features of spinal cord injury are associated with development of severe autonomic dysreflexia?
Complete (rather than incomplete) spinal cord injury
Higher spinal cord lesions more severe
Usually >1 year after injury
What are the mechanisms of cerebral autoregulation?
Metabolic - balance between demand and supply; vasoactive substances
Myogenic - transmural pressure
Neurogenic - vascular smooth muscle resistance via autonomic innervation
Where can aneurysms form? Where is most common?
Anterior communicating (40%) Middle cerebral/internal carotid Posterior communicating
What are the contents of the posterior fossa?
- Brainstem (midbrain, pons, medulla)
- Cerebellum
- Fourth ventricle
- Cranial nerves
What are the PRE-OP considerations for anaesthetising a patient for posterior fossa surgery?
- Documentation of deficits/evaluation of cranial nerves
- Assess for presence of raised ICP
What are the INTRA-OP considerations when anaesthetising a patient for posterior fossa surgery?
Positioning - ETT/prone/pressure
Blood loss - sinuses
BP instability - brainstem, arterial line
Facial nerve monitoring - TIVA
How to give a Posterior Fossa anaesthetic:
- Monitoring PLUS arterial line
- Prepare for massive blood loss (and sudden too!)
- TIVA with Remi
- Facial nerve monitoring may be required (depending on tumour location etc e.g. acoustic neuroma)
- Reinforced ETT
- Positioning - prone/lateral/park bench
- Mayfield clamp - stimulating
- Cardiovascular instability when handling brainstem
- Smooth extubation
What are the POST-OP considerations for posterior fossa surgery?
- HDU post op
- Any new lower cranial nerve dysfunction will put them at risk for aspiration
- Highly emetogenic - lots of anti-emetics prescribed
- More painful than supratentorial surgery
What is an acoustic neuroma?
A vestibular schwannoma
- Benign tumour of myelin-forming Schwann cells of 8th cranial nerve
- Clinical features - unilateral hearing loss, tinnitus, vertigo
- If large: Trigeminal or Facial nerve features
What are the normal CSF pressure waves and how do they relate to the cardiac cycle?
P1 > P2 > P3
A waves: pathological, high amplitude
B waves: rhythmic oscillations, mechanically ventilated patients
C waves: low amplitude, non pathological
(See “Monitoring the brain”)
What is the normal range of ICP for adults and infants?
10-15mmHg
3-4mmHg
Describe the types of ICP waves
A waves
B waves
C waves
How do you measure ICP?
Invasively:
—ICP bolt
—EVD
Non-invasively: —History of symptoms/change in symptoms —Papilloedema —CT/MRI —USS of optic sheath diameter
How can cerebral metabolism be monitored?
…
What are the different spinal cord protection strategies undertaken during thoracoabdominal aneurysm repair?
- Mild systemic hypothermia (32 - 34)
- Maintaining Spinal Cord Perfusion Pressure (SCPP = MAP - CSFP) by pushing up MAP or lumbar drains for decreasing CSFP
- Distal aortic shunt through fem-fem/L heart bypass
- Pharmacological neuroprotection - free radical scavenging, steroids
- Monitoring spinal cord function with MEPs/SSEPs
What are the afferent and efferent cranial nerves used for brain stem death testing?
Pupillary light reflex - II / III
Corneal reflex - V / VII
Supraorbital pain stimulus - V / VII, XI
Vestibulo-ocular - VIII / III, IV, VI
Gag reflex - IX / X
Cough reflex - X / X
What are the indications/preconditions for brainstem death testing?
Apnoeic coma
Clear diagnosis of underlying cause
How is oxygenation maintained during apnoea testing?
Pre-oxygenate
Oxygen via catheter in ETT
Apnoeic mass transfer of O2 (by 250ml/min removal of O2 from FRC with only 10ml CO2 added = 240ml drawn down)
What supportive tests are useful in brainstem death testing?
Cerebral angiography - MR/CT Transcranial Doppler EEG PET Evoked potentials
How would you anaesthetise someone for scoliosis surgery?
Pre-op:
—Assessment of restrictive lung deficit & RV function - ECHO and spirometry
—Comorbidities - especially if associated condition (e.g. neuromuscular syndromes)
Intra-op:
—TIVA
—Spinal cord monitoring (reduces risk from 5% to 0.5% of damaging cord)
—Invasive monitoring - A-line/urinary catheter/IV access
—Positioning (prone)
—Reinforced ETT
—Blood loss preparation & TXA
—Attention to warming - high risk of heat loss
Post-op:
—HDU
—Good analgesia - paracetamol/NSAIDS/ketamine/Mg/IV lidocaine/opioid PCA/epidural catheter by surgical team
—Good PONV prevention
Describe the analgesic regime for patients undergoing scoliosis surgery
Multimodal: —IT opioids —PCA —NSAIDs —Paracetamol —Intraoperative remifentanil —Intraoperative/postoperative ketamine infusion —Magnesium
Control PONV
Keep warm
How can you measure CSF pressure?
Directly:
—Lumbar Puncture
—Lumbar drain
—Intra-parenchymal sensor
Indirectly:
—Patient report
—Imaging
Normal CSF pressure is 10-15mmHg
How can you measure cerebral oxygenation?
Jugular venous SpO2
NIRS
Brain tissue oxygenation
How can you measure Cerebral Blood Flow?
Transcranial Doppler
CT/MRI perfusion scans
What is the difference between Serotonin Syndrome and Neuroleptic Malignant Syndrome?
Serotonin Syndrome:
—Rapid onset; rapid improvement
—Hyperreactivity: tremor/clonus/hyperreflexia
—Treated with benzos
NMS:
—Slow onset
—Bradyreflexia, rigidity
—Caused by dopamine antagonist OR withdrawal of dopamine agonists
—Treated with bromocriptine; could use dantrolene
—Slow resolution
—Higher mortality than SS
What is neurofibromatosis?
Autosomal dominant
Type 1:
—intellectual impairment, neural tumours, scoliosis, phaeochromocytoma, cardiomyopathy
Type 2:
—bilateral acoustic neuroma, cataracts, neural tumours
What trial looked at decompressive craniectomy?
DESTINY trial looked at decompressive craniectomy in malignant MCA syndrome in patients >60years old
What grading system is used in diffuse axonal injury?
Marshall grading system (1-4)
Midline shift of >5mm = Grade 4
What factors affect cerebral blood flow?
Those affecting:
—Cerebral Perfusion Pressure:
-MAP
-ICP
-CVP
—Radius of cerebral vessels:
-Myogenic control
-Metabolic mediators: pCO2, pO2, CMRO2, Temp
-Neurogenic mediators
-Endothelial mediators
-Chemical mediators: volatile or IV anaesthetic agents
—Affecting blood rheology:
-Haematocrit
What are the Schwartz-Bartter criteria for SIADH?
- Hyponatraemia with hypo-osmolar
What grading systems are there for SAH?
Scored at presentation
WFNS:
1. GCS 15 without focal deficit
2. GCS 13-14 without deficit
3. GCS 13-14 with deficit
4. GCS 7-12
5. GCS <7
Fisher:
1. No SAH
2. No clots, thin SAH
3. Clots, blood layer >1mm
4. ICH/IVH present; diffuse or no SAH
What is the indication for mechanical thrombectomy in stroke?
Within 24 hours of stroke onset
Patients with:
-large vessel occlusion (carotid/MCA/basilar)
-good pre-morbid state (mRs 0-2)
-NIHSS >6
-ideally within 6 hours
Aim BP 140-180mmHg
