General Neurology Flashcards
What neural tissue is the nervous system derived from?
• Nervous system derived from ectoderm
Outline the brief derivation of the nervous system.
• Ectoderm –> Neural plate –> Neural tube closes –> Neural crest cells give rise to NS cells: Melanocytes, Schwann Cells, Adrenal medullary cells, dorsal root ganglion cells, autonomic ganglion cell
List the broad components of the nervous system.
- Cells
- Connective Tissue
- Blood vessels
List the two cellular categories of the nervous system.
- Neurons
* Glial cells
Give 3 examples of glial cells and outline their roles.
• Oligodendrocytes: myelination formed by these cells which is a spiral multi-layered wrapping of glial membrane increasing AP conduction speed by restriction of ionic current to smaller unmyelinated portions at nodes of Ranvier
- 1 oligodendrocyte to many myelinated CNS axons
• Microglial cells: Immune responses within CNS removing cellular products by phagocytosis assisted by other glia and phagocytes invading CNS from circulation
• Astrocytes: named by morphology with cell body and several branches arising which produces BBB, regulates the CNS microenvironment by buffering EC environment with ions and NTs, local astroglia take up excess K+, post-injury astrocytes ∆ to become reactive astrocytes forming glial scar (segregating damaged tissue) and couples GAP junctions to form sanctum for small molecules and ions to redistribute along concentration gradients or by current glow.
• Ependymal cells: epithelium lining ventricular spaces of the brain which secretes CSF in ventricular system where the substance diffuses readily across ependymal lining between EC space of brain and CSF
• Satellite cells: encapsulate dorsal root and cranial nerve ganglion cells regulating microenvironment like astrocytes
What is the role of oligodendocytes?
myelination formed by these cells which is a spiral multi-layered wrapping of glial membrane increasing AP conduction speed by restriction of ionic current to smaller unmyelinated portions at nodes of Ranvier
- 1 oligodendrocyte to many myelinated CNS axons
What is the role of microglial cells?
Immune responses within CNS removing cellular products by phagocytosis assisted by other glia and phagocytes invading CNS from circulation
What is the role of astrocytes?
named by morphology with cell body and several branches arising which produces BBB, regulates the CNS microenvironment by buffering EC environment with ions and NTs, local astroglia take up excess K+, post-injury astrocytes ∆ to become reactive astrocytes forming glial scar (segregating damaged tissue) and couples GAP junctions to form sanctum for small molecules and ions to redistribute along concentration gradients or by current glow.
What is the role of ependymal cells?
epithelium lining ventricular spaces of the brain which secretes CSF in ventricular system where the substance diffuses readily across ependymal lining between EC space of brain and CSF
What is the role of satellite cells?
encapsulate dorsal root and cranial nerve ganglion cells regulating microenvironment like astrocytes
List the 3 structural features of a neurone.
1) Dendrites: branching extensions of soma which expands SA of neurone
2) Soma (cell body): core of neurone bearing genetic and metabolic centres of neurones
3) Axon: extension of cell body, as proximal dendrite in specialised region called axon hillock, conveying output of cell to other neurones with variable length and diameter ∆s according to neuronal type.
Describe what a dendrite is?
Dendrites: branching extensions of soma which expands SA of neurone to receive signals from other neurones which can be primary or higher-order. Individual dendrites aggregate into dendritic trees ≈ ∆ between different neurone types, size, number and spatial organisation
What is a soma? List 3 cellular organelles it contains.
core of neurone bearing genetic and metabolic centres of neurones” nucleus, nucleolus, Nissl bodies (neuronal biosynthetic apparatus ≈ RER + Golgi Body), mitochondria, cytoskeletal elements). Soma receives synaptic input from dendrites
What is an axon? List the cellular organelles it may contain.
extension of cell body, as proximal dendrite in specialised region called axon hillock, conveying output of cell to other neurones with variable length and diameter ∆s according to neuronal type. Axon is absent of RER, free ribosomes and Golgi apparatus. Axon may terminate in a synapse and may make synapses along its length.
Define radial migration.
- Cells migrate along radial glia from origin in ventricular and subventricular zones –> formation of cortex and deep nuclear structures
- Radial migration gives rise to projection neurons of the cortex
Give an example of the process of nerve cell migration in the brain.
Radial Migration:
• Cells migrate along radial glia from origin in ventricular and subventricular zones –> formation of cortex and deep nuclear structures
• Radial migration gives rise to projection neurons of the cortex
List the 4 lobes of the brain and their functions.
1) Frontal lobe: Motor functions and Personality and ability to change; ‘frontal lobe personalities’
• Sequencing and fluency
2) Temporal lobes: Memory and speech (L > R)
3) Parietal lobe: Spatial awareness ( R ), Language (L)
4) Occipital lobes: Vision
Based on the 4 lobes of the brain and their function, outline a quick functional test for each lobe.
1) Frontal lobe: Motor functions and Personality and ability to change; ‘frontal lobe personalities’
• Sequencing and fluency
Test(s):
• Name as many animals in 1 minute or words beginning with FAS
• Luria hand-sequencing task: Repeat back hand sequence
2) Temporal lobes: Memory and speech (L > R)
Test(s):
• Address test: Give a pseudo address and see if they remember it
• Object recall
• Serial 7s
3) Parietal lobe: Spatial awareness ( R ), Language (L)
Tests: • Clock face: Put numbers on and draw ten to two, neglecting one side of space, put all on one side • Naming objects • Drawing cube, interlocking infinity • Agnosia
4) Occipital lobes: Vision
Outline the visual field pathway.
• Light -> photoreceptors (rods and cones) -> retinal ganglion cells -> leaves orbit via optic canal (passageway between sphenoid bone) -> enters cranial cavity running along surface of middle cranial fossa -> optic nerves from each eye unite ≈ optic chiasm -> fibers from nasal (medial) half of each retina cross over to contralateral optic tract whilst temporal (lateral) halves remain ipsilateral -> Optic tract (L+R) -> synapse in lateral geniculate nucleus (LGN) relay system in thalamus -> axons from LGN carry visual information in optic radiation pathway (upper optic radiation and lower optic radiation) ->
i) Upper optic radiation: Fibres from superior retinal quadrants (correspond to inferior visual field quadrants) travel through parietal lobe to reach visual cortex
ii) Lower optic radiation: Fibres from inferior retinal quadrants (correspond to superior visual field quadrants) travel through temporal lobe via Meyers’ loop pathway to reach visual cortex
How much protein is in CSF?
• Protein free
Where is CSF derived from?
• Plasma-derived
How much CSF is present in the body?
• 120-150ml
How much CSF is produced per day and how is this removed?
- Constant production: 500ml day
* Reabsorbed in arachnoid granulations in venous sinsuses and nasal
Where is CSF reabsorbed?
• Reabsorbed in arachnoid granulations in venous sinsuses and nasal lymphatics
List the general components of CSF.
- No RBC
- Low WBC <5/ml
- Protein (low) < 0.5mg/ml
- Glucose: 60-70% blood levels ≈ 2.5-5mmol/L)
List 5 functions of CSF.
- Buoyancy (weighs less)
- Protection: soft gel in hard box
- Waste clearance
- Homeostasis
- Intracranial pressure regulation
- Immune surveillance
Outline the ventricular system of the brain.
set of four interconnected cavities in the brain where CSF is produced (choroid plexus bearing ependymal cells).
1) Lateral ventricle @ cerebral hemisphere
2) Central ventricle @ spinal cord
3) 3rd ventricle @ Diencephalon via aqueduct
4) 4th ventricle @ Brain stem
5) Arachnoid Granulations (in venous sinuses): Reabsorbed
Outline the key features of a lumbar puncture.
- Lying left lateral with legs flexed at knee and pulled towards their chest (foetal position)
- Clean with iodine + inject with anesthetic
- Feel for ASIS (L3/L4)
- Lumbar puncture needle, withdraw central core
- Connected to manometer
What is a normal reading for a lumbar puncture.
• OP <20cm = normal OP
List the 3 reading categories for a lumbar puncture.
- OP <20cm = normal OP
- 21-29 = intermediate
- > 30 cm water = elevated
Outline the complications of a lumbar puncture.
- Headache: Low pressure headache, worse standing up, eased lying down, N+V
- Bleeding/bruising
- Nerve damage
- Infection
- Coning/Death
What 3 general scenarios are there regarding the blockage and accumulation of CSF.
- Unfused cranial sutures: Expanded cranium
- Fused cranial sutures: Occurs slowly ≈ normal
- Fused cranial sutures: Occurs rapidly
List the general pathological causes of elevated CSF.
Congenital
Acquired • Infections • Inflammation • Tumours: Malignant meningitis • Vascular
Outline an intervention to manage a raise in ICP due to accumulation of CSF.
• Ventriculoperitoneal shunt (VPS)
Which two groups of people are more likely to suffer from Idiopathic Intracranial Hypertension? (IHH)
- Female > Male
* Usually Overweight
List 3 signs (general or specific) of raised intracranial pressure.
- Symptoms of raised ICP
- Visual disturbances
- Diplopia
• Papilloedema
List the main concern regarding complication of IIH.
• Blindness (check visual acuity and fields)
Give two investigations you would order in a patient with IHH.
- MRV
* Lumbar puncture: Raised pressure in 30cm/40cm
Outline the management for IHH.
- Supportive: Weight loss and analgesics
- Acetazolamide: reduce production of fluid in the eye (CA inhibitor)
- Repeated LP: Remove some of the CSF
- Shunt: Ventriculoperitoneal shunt
Outline key points about low pressure headaches.
Low Pressure Headaches • Eased on lying down • Worse on standing up • Occur spontaneously (v. rare) • Usually post-LP
Outline the disease of syringomyelia. Signs and symptoms; Investigations and Management.
= fluid-filled cavity or cyst (syrinx) forms within spinal cord. Expanding syrinx compresses and destroys surrounding nervous tissue.
Signs and Sx: • Neck and shoulder pain • Muscle weakness • Pain • Stiffness in legs • Numbness • Decreased sensation • Scoliosis • Ataxia
Investigations:
• MRI: Chiari malformation
Management:
• Supportive
What occurs if a syrinx is in the medial tract?
Syrinx is in medial tract ≈ affecting spinothalamic tracts where nerve fibres cross with LMN problems in hand (distance to synapse) and UMN problems in legs (distance to synapse)
Outline important areas to cover in a meningitis history.
- Exposure
- Petechial rash
- Recent infection
- Recent travel – endemic regions?
- History of IVDU
- History of recent or remote head trauma
- Otorrhea or rhinorrhea
- HIV infection or risk factors
- Immunocompromising conditions
Outline key features in the presentation of meningitis.
- Stiff neck**
- Altered mental state (confusion, delirium, drowsiness, impaired consciousness)
- Non-blanching rash
- Bulging fontanelle (infants)
- Photophobia (Meningiococcal disease)
- Kernig’s Sign
- Brudzinski’s Sign
- Coma
- Paresis
- Focal neurological deficit
- Seizures
Constitutional: • Fever • Nausea • Vomiting • Lethargy • Irritable • Anorexia • Headache • Muscle ache • Joint pain • Cough
What is a key differentiating symptom for the diagnosis of meningitis.
• Stiff neck**
Give considerations for a patient presenting with potential bacterial meningitis.
- Age of patient
- Vaccination status
- Immune status – primary or acquired immunodeficiency
What is the importance of the Blood-brain barrier?
BBB prevents fluctuations in nutrients, metabolites or blood-borne substances ≈ regulated environment + homeostasis ≈ protection of brain from systemic events regulated by tight junctions + astrocyte processes contact vessel from neuropil side ≈ separates blood compartment from neuropil compartment. Transport across BBB limited to small lipophilic molecules, water and gases with other substances requiring active transport.
What is the main method of neuronal communication and where does this occur?
Neurones communicate via synapses which occurs between axons and dendrites either by direct electrical communication or neurotransmitter diffusion to propagate the electrical charge (action potential)
What is a ganglion? What is a nucleus? How do ganglions and nucleus differ?
Ganglion: Collection of nerve cell bodies outside the CNS
Nucleus: Collection of nerve cell bodies inside the CNS
What are the two gross appearances of the nervous system? What are the differences between these?
1) Grey Matter: Cell bodies of neurones + neuroglia + unmyelinated neurones
• Nucleus (CNS)
• Ganglion (PNS)
• Surface of cerebral and cerebella hemispheres
Locations:
• Brain: Grey matter outside
• Spinal cord: Grey matter in centre
2) White Matter: Axons of myelinated neurones.
Locations:
• Brain: White matter is central
• Spinal cord: White matter is peripheral
What are the regions of the central nervous system?
- Spinal cord
- Brainstem (nuclei of all CN bar CN I + CN II)
a) Medulla
b) Pons
c) Midbrain - Cerebellum
4. Cerebrum
a) Telencephalon (cerebral hemispheres)
b) Diencephalon (thalamus + hypothalamus)