W10: Eye Pathology; NS Pathology; Neurology; Neurovasc.; Neurosurgery Flashcards
principles behind investigations such as FFA, OCT, ERG, EOG and VEP.
FFA: normal fluorescence of optic nerve; Na fluorescein;
Optical Coherence Tomography (OCT): measures input waves (neurosensory img of retina); macular disease.
ERG: electroretinogram (ERG) is a diagnostic test that measures the electrical activity of the retina in response to a light stimulus. The ERG arises from currents generated directly by retinal neurons in combination with contributions from retinal glia
electroocoulogram (EOG) is an elecrophysiologic test that measures the existing resting electrical potential between the cornea and Vitreous membrane. Normal Retinal pigment epithelium is 6 millivolts (mV)
Visual Evoked Potentials (VEPs) testing measures the signals from your visual pathway
Describe the retinal diseases that lead to sudden painless loss of vision
Central retinal arterial occlusion
Branch retinal art. occlusion
central vein occlusion
-retinal haemorr. | -swelling: macula + optic nerve
=> intravitreal anti-VEGF
Art. ischaemic optic neuropathy (AION)
-ARTERITIC: giant cell arteritis (temporal art.)
*headache, scalp tenderness, loss of appt., pain on chewing
=> systemic steroids
-NON-ARTERITIC: painless (NAION)
=> RF (aspirin e.g.)
Describe the retinal conditions that cause gradual painless loss of vision
CATARACTS: lens opcaficiation +dazzle/glare
=>sx; phacoemulsification w/ intraoc lens implant
DM RETINOPATHY: microaneurysms,retinal haemorr. etc. | fluorescein OCT
=> intravitreal antiVEGF; Laser panretinl photocoag., AIDS
GLAUCOMA: optic neuropathy w/ optic nerve dmg. peripheral vis loss. intraoc. pressure
*open/closed angle | chronic / acute
=>topical
=> Trabeculectomy
MACULAR DEGEN. (AGE-RELATED):calcification @ macula, progressive central vis. loss.
- octomography: oedema ID, fluoro ID leakage
*neovasc. @ choroid + pigment changes
*advanced: atrophy => loss of vis.
=>antiVEGF
=> low vision aids
Elaborate on the retinal appearance in central retinal artery or central retinal vein occlusion
CRAO:
It usually causes sudden loss of eyesight in one eye.
retinal whitening and a cherry red spot are due to opacification of the nerve fiber layer as it becomes edematous from ischemia. The fovea is cherry red because it has no overlying nerve fiber layer
A branch retinal vein occlusion occurs when part of this branch vein system is blocked. A blockage causes backpressure and leads to hemorrhaging, exudation, and/or decreased blood flow in the area of the retina drained by that particular branch retinal vein.
Understand how optic neuritis and ischaemic optic neuropathy develop
optic neuritis: arises from auimm attack of myelin
ischaemic neuropathy: inflamm of vasc and RF HT, hyperglycaemia, DM
Give a differential diagnosis for conditions that cause a Red Eye
ALLERGIC CONJUNCTIVITIS:itchy mucoid discharge, lid swelling, CHEMOSIS (conj. swelling)
=> topical antihistamines
INFECTIVE CONJUNCTIVITIS: gritty discharge
=> topical abx
CORNEAL ABRASION: pain/watering
=> topical abx + analgesia
SCLERITIS: systemic AuIm. pain++ tender++, deep vessels.
*nodule
=> systemic steroids
ACUTE ANTERIOR UVEITIS: iris+cilliary body inflamm
*photophobia, floaters, pain
*HYPOPYON - wbc sedimentation
=> topical steroids
=> dilating drop (prevents posterior synechei complication - attachment to lens capsule + prevent dilatation)
Hallmarks of orbital cellulitis
orbital tissue infection. often visual +systemic illness/SEPSIS
=> IV abx / urgent CT drainage
Watershed cerebral infarctions
Watershed cerebral infarctions, also known as border zone infarcts, occur at the border between cerebral vascular territories where the tissue is furthest from arterial supply and thus most vulnerable to reductions in perfusion
Causes of generalised interruption
HYPOXIA w/ intact circulation: CO2 poisoning, resp arrest
INABILITY TO USE O2: cyanide, CO
ISCHAEMIA: cardiac arrest (partial/complete cortical necrosis); brain swelling (trauma); HypoT + Shock
Encephalitis
Viral ∴ slower pres.
- HSV >CN V. (latent) =>ACICLOVIR
- Arbovirus; travel hx (animal vector)
flu prodrome > progressive headache + fever
+meningism +!temporal/memory dysf.
- lymphocytosis, normal glucose, (+) protein, mononuclear
- transitory PLEDS EEGs
Meningitis
Nisseria men. (meningococcous)
Strep. pneumon. (pneumococcus) => peniccillin sens
Enteroviruses (faecooral) > non-paralytic men.
FEVER-STIFF NECK-ALTERED MENTAL. => confusion+delirium
+ etc. (photo, petichial rash, headache)
- cultures, lumbar, CT
- ↑pressure, neutropenia, hypoglycaemia, (++) protein
=>CEFTRIAXONE
BRAIN ABSCESS + EMPYEMA
Polymicrobia, (bact. endocarditis!), trauma, infection spread (dental, sinus, ear)
IMAGING Dx +biopsy +culture
=> Penicillin / Ceftriaxone
=> Metronidazole
=> Sx drain
!HIV
- toxoplasmosis
- aseptic meningitis
- 1º cerebral lymphoma
- fungal (cryptococcal) men.
Describe the use of passive and active immunisation to prevent neurological disease
RABIES: paraesthesia, ascending paralysis, animal bite
=> select vax. | HUMAN RABIES Ig (passive)
TETANUS: soil spore toxin release. blocks motor inhibition = rigid + spasm
=> TOXOID VAX. + Ag. | Penicillin + Ig.
BOTULISM: infantile, food borne, IVDU
irreversible binding = ACh block @ autonomic nerve junction
=> anti toxin / penicillin / wound debdridement
Post infective inflamm syndromes
Think: children
Acute Disseminated Encephalomyelitis (ADEM):
Post-infective. AuIm attack of myelin sheath.
•nausea and vomiting, headache, irritability and sleepiness, unsteadiness or inability to walk, problems with vision, weakness or tingling in certain areas of the body
Guillain-Barre Syndrome: AuIm attack on peripheral nerves => pins needles, weakness, numb., balance and co-ord
Creutzfeldt–Jakob disease
prion.
sporadic, familial acquired
- rapid dementia, insidious
- MYOCLONUS (sudden twitching jerking)
- global decline
~6mos
•MRI
=> supportive tx
Discuss epidemiology and aetiology of head injury
SKULL FRACTURES •contre-coup • depressed fracture: men. risk • linear > hinge fracture •mosaic •ring fracture
INTRACRANIAL INJURIES
• EDH: outer dura-skull. d/t skull fracture MMA tear
-fast. sport. young.
• SDH: tear of bridging veins nil fracture
slow venous.
• SAH: beneath arachnoid. natural disease - berry aneurysm.
-trauma: contusion
INTRINSIC BRAIN INJURIES
CEREBRAL CONTUSION: surface bruises
cerebral laceration
DIFFUSE AXONAL INJURY: microscopic dx, blobs. vasc injury.
Coup + Contracoup
List the clinical conditions that can cause raised intracranial pressure and the body’s physiological response to such an insult
- morning headache + sickness (brainstem)
- papilloedma (optic nerve)
- pupillary dilatation (CN III)
- ↓Glasgow (cortex+brainstem)
- Brainsteam death (coning)
Understand how raised ICP can lead to subfalcine, tentorial and brainstem herniation
Increased pressure = shift of tissue
=> subfalcine herniation: herniation under falx cerebri, crushing lateral ventricles + midline shift
+ tentorial herniation + brainstem herniation
