PBL Learning Objectives Flashcards
Anatomy of the vertebral column, spinal cord and meninges (8.1)
Spinal tracts (ascending and descending) (8.1)
Causes of acute onset paralysis (8.1)
GBS, transverse myelitis, myasthenia gravis, polio, muscle diseases, botulism, ADEM, cord compression
Autonomic nervous system (arrangement, outflow and function) (8.1)
Sympathetic: Cells bodies within the lateral horns of levels T1-L2. Exit via the white ramus commicantes to enter the sympathetic chain. May synapse within the sympathetic chain or at distal ganglia.
Parasympathetic: Arises from cranial nerves (III, VII,IX and X) and S2-S4.
Causes of acute onset sensory loss (8.1)
- Stroke
- Spinal cord compression
- Multiple Sclerosis
- Diabetes Mellitus
- Hypothyroidism
- Vitamin B1, B6, B12 or E deficiency
Peripheral motor and sensory pathways (reflex circuits) (8.1)
Myotactic reflex - Knee jerk (muscle spindle)
Golgi tendon reflex
Flexor reflex
Crossed extension reflex
Anatomy of the meninges (8.2)
Extra dural space
Dura matter (periosteal and meningeal layers)
- Reflections of the meningeal layer form the tentorium cerebelli, falx cerebri and falx cerebelli
- The dural venous sinuses are formed by separations of the periosteal and meningeal layers - structure and names
Epidural space
Arachnoid matter
Subarachnoid space
Pia matter
Blood supply: Middle meningeal artery (from external carotid)
The Dura is innervated by branches of the trigeminal, glosspharyngeal and vagus nerves (V, IX and X). The high degree of overlap provides potential for referred pain.
Anatomy of the skull (8.2)
Bones of the skull, areas of importance, possible pathologies
Host response to infection (8.2)
The innate immune reponse initiates the sequence. The innate immuen system is non-adaptable and is ‘non-specific’ in its response (same response seen to multiple pathogens).
Recognition of foreign material through PAMP:PRR interactions.
Release of pro-inflammatory cytokines and complement induced inflammation.
Complement allows for opsonisation, neutralisation and/or cell lysis (via MAC).
Inflammation sees vasodilation (NO), increased vessel permeabilty (histamine) and formation of inflammatory exudate (rich in Igs and complement proteins).
Neutrophils are recruited to the site of damage/infection. Adhesion molecules (selectins, integrins etc) allow for extravasion.
Macrophages and leukocytes are later recruited - adaptive immunity.
Outcomes of inflammation include resolution, repair by fibrosis (loss of function), chronic inflammation (inflammation and repair occuring simultaneousy) and abscess formation.
T1 vs T2
Microbiology of meningitis and CNS infection (8.2)
Normal and abnormal CSF circulation (8.2)
Normal:
Lateral ventricles → cerebral aqueduct → third ventricle → intraventricular foramen → fourth ventricle → 2 x lateral and medial aperture → CSF enters the subarachnoid space → reabsorbed by arachnoid granulations → enters the dural venous sinus
Abnormal CSF circulation - Hydrocephalus: Increased CSF volume, dilation of the ventricles +/- raised intracranial pressure
Communication hydrocephalus: Decreased CSF absorption by arachnoid granulations. Increased ICP, papilloedema and herniation
Normal pressure hydrocephalus: Idiopathic, seen in the elderly. Dispansion of the ventricles disrupts the corona radiata leading to ‘wet, wobbly and wacky’ symptoms (incontinence, ataxia and cognitive dysfunction)
Non-communicating (obstructive) hydrocephalus: Structural blockage of the ventricles (e.g. colloid cyst)
Meningitis vaccination programme (8.2)
Meningitis B Vaccine
6-in-1 vaccine: Protects against Haemophilus influenzae type B (Hib), an organism that can cause meningitis
Pneumococcal vaccine: Protects against meningitis
Hib/Men C vaccine
MMR vaccine: Meningitis often occurs as a complication of these conditions
Meningitis ACWY vaccine: Protects against meningococcal groups A, C, W and Y which cause meningitis
Symptoms and sign of meningitis (8.2)
Signs and symptoms of bacterial meningitis:
- Fever
- Severe headache
- Neck stiffness
- Photophobia
- Altered mental state
- Vomiting seizures
- Nuchal rigidity: A stiff neck with resistance to passive flexion
- Rash: Primarily associated with meningococcal meningitis
- Signs of raised ICP: Papilloedema, bulging fontanelle
- Evidence of a primary source of infection: Pt may have had sinusitis, pneumonia, otitis media or mastoiditis
- Positive Kernig’s and Brudzinski’s signs
Viral meningitis signs and symptoms
- Often self-limiting with no serious sequelae
- Similar presentation to bacterial meningitis
Antimicrobrial treatment of bacterial meningitis (8.2)
If identified in the community, prior to transfer to hospital administer benzylpenicillin.
> 1 month, < 50 years of age
1st line: Dual antibiotic therapy of vancomycin + ceftriaxone/cefotaxime
Adjunct: Supplemental oxygen
Adjunct: Dexomethasone - Reduces rates of hearing loss and neurological sequelae
Lumbar puncture - indications and contraindications (8.2)
Indications: Suspected CNS infection e.g. meningitis, encephalitis (presents with altered mental state), suspected subarachnoid haemorrhage
Contraindications: Unresolved coagulopathy, signs of raised ICP (papilloedema, bulging fontanelle, drowsiness, diplopia), infection at the LP site
Immunological conditions pre-disposing to infection (8.2)
- HIV
- SKID
- Transplantation
- Immunosuppressive therapy e.g. systemic corticosteroids
- Thymus disorder
Long term sequelae following meningitis (8.2)
- Cognitive, behavioural and academic problems
- Hearing loss (sensorineural - 25 - 35 % of pts following pneumococcal meningitis)
- Seizures
Complications include: Shock, coagulopathy, endocarditis and pyogenic arthritis
Management of sepsis and meningitis (8.2)
Altered consciousness and epilepsy (8.3)
Cortical localisation of function (8.3)
(Brodmann’s areas and homunculus)
Risk factors for TIA and stroke (8.3)
Hypertension
Age ( > 55)
Diabetes
Atrial fibrillation (formation of emboli)
High cholesterol levels
Obesity
FHx
Increased oestrogen levels (oestrogen promotes coagulation)
Smoking
Aetiology of epilepsy (8.3)
Epilepsy describes an increased propensity for the hypersynchronus discharge of seizures, leading to seizures.
Epilepsy may be resultant of structural malformations (tumours, scars) or may be congenital (channelopathies, abnormal cortical neural networks).
Differential signs of epilepsy, stroke and psychiatric disease (8.3)
Classification of seizures (8.3)
Space occupying lesions (8.3)
Consequences
Tumours (primary or secondary/metastatic)
Vasculature: Haematoma, aneurysms, stroke & TIAs,
Inflammatory: Abscesses, tuberculoma
Parasitic
Consequences:
- All cause intracranial pressure to increase
- The cranial tissue (cerebrum and ventricles) becomes distorted and displaced by the lesion
- The function of the neural tissue is disrupted and seizure activity may result
Usefulness of tests in diagnosing epilepsy (8.3)
Anti-epilepsy drugs (8.3)
Sodium valporate: Inhibits the metabolism of GABA; inhibits Na+ and Ca2+ channels. Potentiates the inhibitory effects of GABA
Carbamazepine: Inhibits Na+ channels
Lamotrigine: Inhibits Na+ channels
Phenytoin: Inhibits Na+ channels
Gabapentin: Inhibits Ca2+ channels
Effects of anti-epileptic drugs on foetal development (8.3)
Can greatly increase the risk of foetal congenital malformations.
Sodium valporate:
Spina bifida, atrial septal defect, cleft palate, hypospadias
Increased risk of autism spectrum disorder and long-term developmental disorders
Carbamazepine:
Defects in the neural tube, urinary tract, CV system and cleft palate
Phenytoin:
Cleft palate