Neurology - Anatomy and Physiology (2) Flashcards Preview

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Flashcards in Neurology - Anatomy and Physiology (2) Deck (30):
1

Cerebral arteries—cortical distribution (459)

  • Anterior cerebral artery
  • Middle cerebral artery
  • Posterior cerebral artery

  • Anterior cerebral artery
    • Supplies anteromedial surface
  • Middle cerebral artery
    • Supplies lateral surface
  • Posterior cerebral artery
    • Supplies posterior and inferior surfaces

2

Watershed zones

  • Between anterior cerebral/middle cerebral, posterior cerebral/middle cerebral arteries.
  • Damage in severe hypotension -->Ž upper leg/upper arm weakness, defects in higher-order visual processing.

3

Regulation of cerebral perfusion (459)

  • Brain perfusion relies on tight autoregulation. 
  • Cerebral perfusion is primarily driven by Pco2
    • Po2 also modulates perfusion in severe hypoxia
  • Therapeutic hyperventilation (decreased Pco2) helps decrease intracranial pressure in cases of acute cerebral edema (stroke, trauma) via decreased cerebral perfusion by vasoconstriction.

4

Effects of strokes:
Middle Cerebral Artery (MCA)

  • Type of artery / circulation
  • Area of lesion
  • Symptoms

  • Type of artery / circulation
    • Anterior circulation
  • Area of lesion
    • (1) Motor cortex—upper limb and face.
    • (2) Sensory cortex—upper limb and face.
    • (3) Temporal lobe (Wernicke area); frontal lobe (Broca area).
  • Symptoms
    • (1) Contralateral paralysis
      • Upper limb and face.
    • (2) Contralateral loss of sensation
      • Upper and lower limbs, and face.
    • (3) Aphasia if in dominant (usuallyleft) hemisphere.
      • Hemineglect if lesion affects nondominant (usually right) side.

5

Effects of strokes:
Anterior Cerebral Artery (ACA)

  • Type of artery / circulation
  • Area of lesion
  • Symptoms

  • Type of artery / circulation
    • Anterior circulation
  • Area of lesion
    • (1) Motor cortex—lower limb.
    • (2) Sensory cortex—lower limb.
  • Symptoms
    • (1) Contralateral paralysis—lower limb.
    • (2) Contralateral loss of sensation—lower limb.

6

Effects of strokes:
Lenticulo-striate artery

  • Type of artery / circulation
  • Area of lesion
  • Symptoms
  • Notes

  • Type of artery / circulation
    • Anterior circulation
  • Area of lesion
    • Striatum, internal capsule.
  • Symptoms
    • Contralateral hemiparesis / hemiplegia.
  • Notes
    • Common location of lacunar infarcts, 2° to unmanaged hypertension.

7

Effects of strokes:
Anterior Spinal Artery (ASA)

  • Type of artery / circulation
  • Area of lesion
  • Symptoms
  • Notes

  • Type of artery / circulation
    • Posterior circulation
  • Area of lesion
    • (1) Lateral corticospinal tract.
    • (2) Medial lemniscus.
    • (3) Caudal medulla—hypoglossal nerve.
  • Symptoms
    • (1) Contralateral hemiparesis—upper and lower limbs.
    • (2) Decreased contralateral proprioception.
    • (3) Ipsilateral hypoglossal dysfunction (tongue deviates ipsilaterally).
  • Notes
    • Stroke commonly bilateral.
    • Medial medullary syndrome
      • Caused by infarct of paramedian branches of ASA and vertebral arteries.

8

Effects of strokes:
Posterior Inferior Cerebellar Artery (PICA)

  • Type of artery / circulation
  • Area of lesion
  • Symptoms
  • Notes

  • Type of artery / circulation
    • Posterior circulation
  • Area of lesion
    • Lateral medulla—vestibular nuclei, lateral spinothalamic tract, spinal trigeminal nucleus, nucleus ambiguus, sympathetic fibers, inferior cerebellar peduncle.
  • Symptoms
    • Vomiting, vertigo, nystagmus
    • Decreased pain and temperature sensation from ipsilateral face and contralateral body
    • Dysphagiahoarseness, decreased gag reflex
    • Ipsilateral Horner syndrome
    • Ataxia, dysmetria.
  • Notes
    • Lateral medullary (Wallenberg) syndrome.
    • Nucleus ambiguus effects are specific to PICA lesions.
    • “Don’t pick a (PICA) horse (hoarseness) that can’t eat (dysphagia).”

9

Effects of strokes:
Anterior Inferior Cerebellar Artery (AICA)

  • Type of artery / circulation
  • Area of lesion
  • Symptoms
  • Notes

  • Type of artery / circulation
    • Posterior circulation
  • Area of lesion
    • (1) Lateral pons—cranial nerve nuclei, vestibular nuclei, facial nucleus, spinal trigeminal nucleus, cochlear nuclei, sympathetic fibers.
    • (2) Middle and inferior cerebellar peduncles.
  • Symptoms
    • (1) Vomiting, vertigo, nystagmus. 
      • Paralysis of face, decreased lacrimation, salivation, decreased taste from anterior 2⁄3 of tongue, decreased corneal reflex. 
      • Face—decreased pain and temperature sensation.
      • Ipsilateral decreased hearing. 
      • Ipsilateral Horner syndrome.
    • (2) Ataxia, dysmetria.
  • Notes
    • Lateral pontine syndrome
      • Facial nucleus effects are specific to AICA lesions.
    • Facial droop means AICA’s pooped.”

10

Effects of strokes:
Posterior Cerebral Artery (PCA)

  • Type of artery / circulation
  • Area of lesion
  • Symptoms

  • Type of artery / circulation
    • Posterior circulation
  • Area of lesion
    • Occipital cortex, visual cortex.
  • Symptoms
    • Contralateral hemianopia with macular sparing.

11

Effects of strokes:
Basilar artery (BA)

  • Type of artery / circulation
  • Area of lesion
  • Symptoms
  • Notes

  • Type of artery / circulation
    • Posterior circulation
  • Area of lesion
    • Pons, medulla, lower midbrain, corticospinal and corticobulbar tracts, ocular cranial nerve nuclei, paramedian pontine reticular formation.
  • Symptoms
    • Preserved consciousness and blinking, quadriplegia, loss of voluntary facial, mouth, and tongue movements.
  • Notes
    • “Locked-in syndrome.”

12

Effects of strokes:
Anterior Communicationg Artery (ACom)

  • Type of artery / circulation
  • Area of lesion
  • Symptoms
  • Notes

  • Type of artery / circulation
    • Communicating artery
  • Area of lesion
    • Most common lesion is aneurysm.
    • Can lead to stroke.
    • Saccular (berry) aneurysm can impinge cranial nerves.
  • Symptoms
    • Visual field defects.
  • Notes
    • Lesions are typically aneurysms, not strokes.

13

Effects of strokes:
Posterior Communicating Artery (PCom)

  • Type of artery / circulation
  • Area of lesion
  • Symptoms
  • Notes

  • Type of artery / circulation
    • Communicating artery
  • Area of lesion
    • Common site of saccular aneurysm.
  • Symptoms
    • CN III palsy—eye is “down and out” with ptosis and pupil dilation.
  • Notes
    • Lesions are typically aneurysms, not strokes.

14

Aneurysms

  • Definition
  • Berry aneurysm 
    • Location
    • Findings
    • Associated with...
    • Other risk factors
  • Charcot-Bouchard microaneurysm

  • Definition
    • In general, an abnormal dilation of artery due to weakening of vessel wall.
  • Berry aneurysm
    • Location
      • Occurs at the bifurcations in the circle of Willis [A].
      • Most common site is junction of the anterior communicating artery and anterior cerebral artery.
    • Findings
      • Rupture (most common complication) leads to subarachnoid hemorrhage (“worst headache of life”) or hemorrhagic stroke.
      • Can also cause bitemporal hemianopia via compression of optic chiasm.
    • Associated with...
      • ADPKD, Ehlers-Danlos syndrome, and Marfan syndrome.
    • Other risk factors
      • Advanced age, hypertension, smoking, race (increased risk in blacks).
  • Charcot-Bouchard microaneurysm
    • Associated with chronic hypertension
    • Affects small vessels (e.g., in basal ganglia, thalamus).

15

Central post-stroke pain syndrome

  • Neuropathic pain due to thalamic lesions.
  • Initial sensation of numbness and tingling followed in weeks to months by allodynia (ordinarily painless stimuli cause pain) and dysaesthesia.
  • Occurs in 10% of stroke patients.

16

Epidural hematoma

  • Type of hemorrhage
  • Definition
  • CT

  • Type of hemorrhage
    • Intracranial hemorrhage
  • Definition
    • Rupture of middle meningeal artery (branch of maxillary artery), often 2° to fracture of temporal bone.
    • Lucid interval.
    • Rapid expansion under systemic arterial pressure -->Ž transtentorial herniation, CN III palsy.
  • CT
    • CT shows biconvex (lentiform), hyperdense blood collection [A] not crossing suture lines.
    • Can cross falx, tentorium.

17

Subdural hematoma

  • Type of hemorrhage
  • Definition
  • CT

  • Type of hemorrhage
    • Intracranial hemorrhage
  • Definition
    • Rupture of bridging veins.
    • Slow venous bleeding (less pressure = hematoma develops over time).
    • Seen in elderly individuals, alcoholics, blunt trauma, shaken baby
    • Predisposing factors: brain atrophy, shaking, whiplash
  • CT
    • Crescent-shaped hemorrhage that crosses suture lines [B].
    • Midline shift.
    • Cannot cross falx, tentorium.

18

Subarachnoid hemorrhage

  • Type of hemorrhage
  • Definition

  • Type of hemorrhage
    • Intracranial hemorrhage
  • Definition
    • Rupture of an aneurysm (such as a berry [saccular] aneurysm, as seen in Marfan, Ehlers-Danlos, ADPKD) or an AVM.
    • Rapid time course.
    • Patients complain of “worst headache of my life (WHOML).”
    • Bloody or yellow (xanthochromic) spinal tap.
    • 2–3 days afterward, risk of vasospasm due to blood breakdown (not visible on CT, treat with nimodipine) and rebleed (visible on CT) [C].

19

Intraparenchymal (hypertensive) hemorrhage

  • Type of hemorrhage
  • Definition

  • Type of hemorrhage
    • Intracranial hemorrhage
  • Definition
    • Most commonly caused by systemic hypertension [D].
    • Also seen with amyloid angiopathy, vasculitis, and neoplasm. 
    • Typically occurs in basal ganglia and internal capsule (Charcot-Bouchard aneurysm of lenticulostriate vessels), but can be lobar.

20

Ischemic brain disease/stroke

  • Definition
  • Stroke imaging
  • Histologic features
    • 12-48 hours
    • 24-72 hours
    • 3-5 days
    • 1-2 weeks
    • >2 weeks

  • Definition
    • Irreversible damage begins after 5 minutes of hypoxia.
    • Most vulnerable—hippocampus, neocortex, cerebellum, watershed areas.
      • Ischemic hypoxia—“hypocampus” is most vulnerable.
    • ​Irreversible neuronal injury.
  • Stroke imaging
    • Bright on diffusion-weighted MRI in 3–30 minutes (highest sensitivity for early ischemia), dark abnormality on noncontrast CT in ~ 12–24 hours.
    • Absence of bright areas on noncontrast CT highly accurate to exclude hemorrhage (contraindication for tPA).
  • Histologic features
    • 12-48 hours: Red neurons
    • 24-72 hours: Necrosis + neutrophils
    • 3-5 days: Macrophages
    • 1-2 weeks: Reactive gliosis + vascular proliferation
    • >2 weeks: Glial scar

21

Hemorrhagic stroke

  • Intracerebral bleeding
  • Often due to hypertension, anticoagulation, and cancer (abnormal vessels can bleed).
  • May be 2° to ischemic stroke followed by reperfusion (increased vessel fragility).
  • Basal ganglia are most common site of intracerebral hemorrhage.

22

Ischemic stroke

  • Definition
  • 3 types
    • Thrombotic
    • Embolic
    • Hypoxic
  • Treatment

  • Definition
    • Acute blockage of vessels -->Ž disruption of blood flow and subsequent ischemia.
    • Results in liquefactive necrosis.
  • 3 types
    • Thrombotic
      • Due to a clot forming directly at the site of infarction (commonly the MCA [A]), usually over an atherosclerotic plaque.
    • Embolic
      • An embolus from another part of the body obstructs a vessel.
      • Can affect multiple vascular territories.
      • Often cardioembolic.
    • ƒƒHypoxic
      • Due to hypoperfusion or hypoxemia.
      • Common during cardiovascular surgeries, tends to affect watershed areas.
  • Treatment
    • tPA (if within 3–4.5 hr of onset and no hemorrhage/risk of hemorrhage).
    • Reduce risk with medical therapy (e.g., aspirin, clopidogrel)
    • Optimum control of blood pressure, blood sugars, and lipids
    • Treat conditions that increase risk (e.g., atrial fibrillation).

23

Transient ischemic attack

  • Brief, reversible episode of focal neurologic dysfunction
  • Last < 24 hours without acute infarction ((-) MRI), with the majority resolving in < 15 minutes
  • Deficits due to focal ischemia.

24

Dural venous sinuses

  • Large venous channels that run through the dura.
  • Drain blood from cerebral veins and receive CSF from arachnoid granulations.
  • Empty into internal jugular vein.

25

Ventricular system

  • Lateral ventricle -->Ž
  • 3rd ventricle -->
  • 4th ventricle Ž-->
  • CSF

  • Lateral ventricle -->Ž 3rd ventricle via right and left interventricular foramina of Monro.
  • 3rd ventricle -->Ž 4th ventricle via cerebral aqueduct (of Sylvius).
  • 4th ventricle Ž--> subarachnoid space via:
    • Foramina of Luschka = Lateral.
    • Foramen of Magendie = Medial.
  • CSF
    • Made by ependymal cells of choroid plexus
    • Reabsorbed by arachnoid granulations
    • Drains into dural venous sinuses.

26

Hydrocephalus

  • Communicating hydrocephalus
  • Normal pressure hydrocephalus

  • Communicating hydrocephalus
    • Communicating (nonobstructive)
    • Decreased CSF absorption by arachnoid granulations, which can lead to increased intracranial pressure, papilledema, and herniation (e.g., arachnoid scarring post-meningitis).
  • Normal pressure hydrocephalus
    • Communicating (nonobstructive)
    • Does not result in increased subarachnoid space volume.
    • Expansion of ventricles [A] distorts the fibers of the corona radiata and leads to clinical triad of urinary incontinence, ataxia, and cognitive dysfunction (sometimes reversible).
    • “Wet, wobbly, and wacky.”

27

Hydrocephalus

  • Hydrocephalus ex vacuo
  • Noncommunicating hydrocephalus

  • Hydrocephalus ex vacuo
    • Communicating (nonobstructive)
    • Appearance of increased CSF in atrophy (e.g., Alzheimer disease, advanced HIV, Pick disease).
    • Intracranial pressure is normal
    • Triad (urinary incontinenc, ataxia, and cognitive dysfunction) is not seen.
    • Apparent increase in CSF observed on imaging is actually result of decreased neural tissue due to neuronal atrophy.
  • Noncommunicating hydrocephalus
    • Noncommunicating (obstructive)
    • Caused by a structural blockage of CSF circulation within the ventricular system (e.g., stenosis of the aqueduct of Sylvius).

28

Spinal nerves

  • Number
  • Where they exit
  • Vertebral disc herniation

  • There are 31 spinal nerves in total
    • 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal.
    • 31, just like 31 flavors of Baskin-Robbins ice cream
  • Where they exit
    • Nerves C1–C7 exit above the corresponding vertebra.
    • All other nerves exit below (e.g., C3 exits above the 3rd cervical vertebra; L2 exits below the 2nd lumbar vertebra).
  • Vertebral disc herniation
    • Nucleus pulposus (soft central disc) herniates through annulus fibrosus (outer ring)
    • Usually occurs posterolaterally at L4–L5 or L5–S1.

29

Spinal cord—lower extent

  • Lower borders
    • Spinal cord
    • Subarachnoid space
  • Lumbar puncture

  • Lower borders
    • In adults, spinal cord extends to lower border of L1–L2 vertebrae.
    • Subarachnoid space (which contains the CSF) extends to lower border of S2 vertebra.
  • Lumbar puncture
    • Lumbar puncture is usually performed between L3–L4 or L4–L5 (level of cauda equina).
    • Goal of lumbar puncture is to obtain sample of CSF without damaging spinal cord.
    • To keep the cord alive, keep the spinal needle between L3 and L5.

30

Spinal cord and associated tracts (465)

  • Corticospinal and spinothalamic tracts
  • Dorsal column

  • Corticospinal and spinothalamic tracts
    • Legs (Lumbosacral) are Lateral in Lateral corticospinal, spinothalamic tracts.
  • Dorsal column
    • Organized as you are, with hands at sides.
    • Arms outside, legs inside.

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