Neurology and Special Senses - First Aid Flashcards
Regional Specification of Developing Brain
- Telencephalon is the 1st part.
- Diencephalon is the 2nd part.
- The rest are arranged alphabetically:
- Mesencephalon
- Metencephalon
- Myelencephalon
Central and Peripheral Nervous Systems Origins:
- CNS Neurons
- Ependymal Cells
- inner lining of ventricles
- make CSF
- Oligodendrocytes
- Astrocytes
Neuroepithelia in Neural Tube
Central and Peripheral Nervous Systems Origins:
- PNS Neurons
- Schwann Cells
Neural Crest
Central and Peripheral Nervous Systems Origins:
Microglia (like macrophages)
Mesoderm
Neural Tube Defects
- Neuropores fail to fuse (4th week) → persistent connection between amniotic cavity and spinal canal.
- Associated with maternal diabetes as well as low folic acid intake before conception and during pregnancy.
- ↑ α-fetoprotein (AFP) in amniotic fluid and maternal serum (except spina bifida occulta = normal AFP).
- ↑ acetylcholinesterase (AChE) in amniotic fluid is a helpful confirmatory test.
Neural Tube Defects:
- failure of caudal neuropore to close, but no herniation
- usually seen at lower vertebral levels
- dura is intact
- associated with tuft of hair or skin dimple at level of bony defect
Spina Bifida Occulta
Neural Tube Defects:
- meninges (but no neural tissue) herniate through bony defect
- associated with spina bifida cystica
Meningocele
Neural Tube Defects:
meninges and neural tissue (eg. cauda equina) herniate through bony defect
Meningomyelocele
Neural Tube Defects:
- also known as rachischisis
- exposed unfused neural tissue without skin/meningeal covering
Myeloschisis
Neural Tube Defects:
- failure of rostral neuropore to close → no forebrain, open calvarium
- Clinical Findings: polyhydramnios (no swallowing center in brain)
Anencephaly
Neurologic Defects:
- failure of left and right hemispheres to separate
- usually occurs during weeks 5–6
- may be related to mutations in sonic hedgehog signaling pathway
- moderate form has cleft lip/palate, most severe form results in cyclopia
- seen in trisomy 13 and fetal alcohol syndrome
- MRI reveals monoventricle and fusion of basal ganglia
Holoprosencephaly
Posterior Fossa Malformations:
- ectopia of cerebellar tonsils (1 structure)
- congenital
- usually asymptomatic in childhood
- manifests in adulthood with headaches and cerebellar symptoms
- associated with spinal cavitations (eg. syringomyelia)
Chiari I Malformation
Posterior Fossa Malformations:
- herniation of low-lying cerebellar vermis and tonsils (2 structures) through foramen magnum with aqueductal stenosis → hydrocephalus
- usually associated with lumbosacral meningomyelocele (may present as paralysis/sensory loss at and below the level of the lesion)
Chiari II malformation
Posterior Fossa Malformations:
- agenesis of cerebellar vermis leads to cystic enlargement of 4th ventricle that fills the enlarged posterior fossa
- associated with noncommunicating hydrocephalus, spina bifida
Dandy-Walker Syndrome
Neurologic Defects:
- cystic cavity (syrinx) within central canal of spinal cord
- fibers crossing in anterior white commissure (spinothalamic tract) are typically damaged first
- results in a “cape-like,” bilateral symmetrical loss of pain and temperature sensation in upper extremities (fine touch sensation is preserved)
- associated with Chiari malformations and other congenital malformations
- acquired causes include trauma and tumors
- most common at C8–T1
Syringomyelia
syrinx = tube, as in syringe
Tongue Development
- 1st and 2nd branchial arches form anterior 2/3 (thus sensation via CN V3, taste via CN VII).
- 3rd and 4th branchial arches form posterior 1/3 (thus sensation and taste mainly via CN IX, extreme posterior via CN X).
- Motor innervation is via CN XII to hyoglossus (retracts and depresses tongue), genioglossus (protrudes tongue, “the genie sticks out his tongue”), and styloglossus (draws sides of tongue upward to create a trough for swallowing).
- Motor innervation is via CN X to palatoglossus (elevates posterior tongue during swallowing).
- Taste—CN VII, IX, X (solitary nucleus)
- Pain—CN V3, IX, X
- Motor—CN X, XII
Neuroanatomy:
- signal-transmitting cells of the nervous system
- permanent cells—do not divide in adulthood
- signal-relaying cells with dendrites (receive input), cell bodies, and axons (send output)
- cell bodies and dendrites can be seen on Nissl staining (stains RER)
- RER is not present in the axon
- injury to axon → Wallerian degeneration—degeneration of axon distal to site of injury and axonal retraction proximally; allows for potential regeneration of axon (if in PNS)
- macrophages remove debris and myelin
Neurons
Neuroanatomy:
- most common glial cell type in CNS
- physical support, repair, extracellular K+ buffer, removal of excess neurotransmitter, component of blood-brain barrier, glycogen fuel reserve buffer
- reactive gliosis in response to neural injury
- derived from neuroectoderm
- GFAP—marker
Astrocytes
Neuroanatomy:
- phagocytic scavenger cells of CNS (mesodermal, mononuclear origin)
- activated in response to tissue damage
- not readily discernible by Nissl stain
- HIV-infected cells fuse to form multinucleated giant cells in CNS
Microglia
Neuroanatomy:
- glial cells with a ciliated simple columnar form that line the ventricles and central canal of spinal cord
- apical surfaces are covered in cilia (which circulate CSF) and microvilli (which help in CSF absorption)
Ependymal Cells
Neuroanatomy:
- ↑ conduction velocity of signals transmitted down axons → saltatory conduction of action potential at the nodes of Ranvier, where there are high concentrations of Na+ channels
- synthesized by oligodendrocytes in CNS (including CN I and II) and Schwann cells in PNS (including CN III-XII)
- wraps and insulates axons: ↑ space constant and ↑ conduction velocity
Myelin
COPS:
- CNS = Oligodendrocytes
- PNS = Schwann cells
Neuroanatomy:
- myelinates only 1 PNS axon
- also promote axonal regeneration
- derived from neural crest
- injured in Guillain-Barré syndrome
Schwann Cells
Neuroanatomy:
- myelinates axons of neurons in CNS
- can myelinate many axons (∼ 30)
- predominant type of glial cell in white matter
- derived from neuroectoderm
- “fried egg” appearance histologically
- injured in multiple sclerosis, progressive multifocal leukoencephalopathy (PML), and leukodystrophies
Oligodendrocytes
Sensory Receptors:
- C—slow, unmyelinated fibers
- Aδ—fAst, myelinated fibers
- all skin, epidermis, some viscera
- pain, temperature
Free Nerve Endings
Sensory Receptors:
- large, myelinated fibers
- adapt quickly
- glabrous (hairless) skin
- dynamic, fine/light touch, position sense
Meissner Corpuscles
Sensory Receptors:
- large, myelinated fibers
- adapt quickly
- deep skin layers, ligaments, joints
- vibration, pressure
Pacinian Corpuscles
Sensory Receptors:
- large, myelinated fibers
- adapt slowly
- finger tips, superficial skin
- pressure, deep static touch (eg. shapes, edges), position sense
Merkel Discs
Sensory Receptors:
- dendritic endings with capsule
- adapt slowly
- finger tips, joints
- pressure, slippage of objects along surface of skin, joint angle change
Ruffini Corpuscles
Peripheral Nerve
- Endoneurium
- invests single nerve fiber layers (inflammatory infiltrate in Guillain-Barré syndrome)
- Perineurium
- blood-nerve permeability barrier
- surrounds a fascicle of nerve fibers
- must be rejoined in microsurgery for limb reattachment
- Epineurium
- dense connective tissue that surrounds entire nerve (fascicles and blood vessels)
Neuropathology:
- reaction of neuronal cell body to axonal injury
- changes reflect ↑ protein synthesis in effort to repair the damaged axon
- characterized by:
- round cellular swelling
- displacement of the nucleus to the periphery
- dispersion of Nissl substance throughout cytoplasm
- concurrent with Wallerian degeneration
Chromatolysis
Neurotransmitter Changes with Disease
Meninges
- Three membranes that surround and protect the brain and spinal cord:
- Dura Mater
- thick outer layer closest to skull
- derived from mesoderm
- Arachnoid Mater
- middle layer
- contains web-like connections
- derived from neural crest
- Pia Mater
- thin, fibrous inner layer that firmly adheres to brain and spinal cord
- derived from neural crest
- Dura Mater
- CSF flows in the subarachnoid space, located between arachnoid and pia mater
- Epidural Space—a potential space between the dura mater and skull containing fat and blood vessels
Blood-Brain Barrier
- Prevents circulating blood substances (eg. bacteria, drugs) from reaching the CSF/CNS.
- Formed by 3 structures:
- Tight Junctions between nonfenestrated capillary endothelial cells
- Basement Membrane
- Astrocyte Foot Processes
- Glucose and amino acids cross slowly by carrier-mediated transport mechanisms.
- Nonpolar/lipid-soluble substances cross rapidly via diffusion.
- A few specialized brain regions with fenestrated capillaries and no blood-brain barrier allow molecules in blood to affect brain function (eg. area postrema—vomiting after chemo; OVLT [organum vasculosum lamina terminalis]—osmotic sensing) or neurosecretory products to enter circulation (eg. neurohypophysis—ADH release).
- Infarction and/or neoplasm destroys endothelial cell tight junctions → vasogenic edema.
- Other notable barriers include:
- Blood-Testis Barrier
- Maternal-Fetal Bood Barrier of Placenta
Neuroanatomy:
- Maintains homeostasis by:
- regulating yhirst and water balance
- controlling Adenohypophysis (anterior pituitary) and Neurohypophysis (posterior pituitary) release of hormones produced in the hypothalamus
- regulating hunger, Autonomic nervous system, temperature, and sexual urges
- areas not protected by blood-brain barrier:
- OVLT (senses change in osmolarity)
- Area Postrema (found in medulla, responds to emetics)
Hypothalamus
TAN HATS:
- Thirst and water balance
- Adenohypophysis
- Neurohypophysis
- Hunger
- Autonomic nervous system
- Temperature
- Sexual urges
Hypothalamus:
- hunger
- destruction → anorexia, failure to thrive (infants)
- stimulated by Ghrelin
- inhibited by Leptin
Lateral Nucleus
Lateral injury makes you Lean.
Hypothalamus:
- satiety
- destruction (eg. craniopharyngioma) → hyperphagia
- stimulated by Leptin
Ventromedial Nucleus
VentroMedial injury makes you Very Massive.
Hypothalamus:
- cooling
- parasympathetic
Anterior Nucleus
A/C = Anterior Cooling
Hypothalamus:
- heating
- sympathetic
Posterior Nucleus
- Heating controlled by Posterior hypothalamus (“Hot Pot”).
- If you zap your posterior hypothalamus, you become a poikilotherm (cold-blooded, like a snake).
Hypothalamus:
circadian rhythm
Suprachiasmatic Nucleus
You need sleep to be charismatic (chiasmatic).
Hypothalamus:
- synthesize ADH and Oxytocin
- ADH and Oxytocin are carried by Neurophysins down axons to posterior pituitary, where these hormones are stored and released
Supraoptic and Paraventricular Nuclei
Hypothalamus:
- thermoregulation, sexual behavior
- releases GnRH
- failure of GnRH-producing neurons to migrate from olfactory pit → Kallmann Syndrome
Preoptic Nucleus
Vomiting Center
- Coordinated by Nucleus Tractus Solitarius (NTS) in the medulla, which receives information from the Chemoreceptor Trigger Zone (CTZ, located within area postrema in 4th ventricle), GI tract (via vagus nerve), vestibular system, and CNS.
- CTZ and adjacent vomiting center nuclei receive input from 5 major receptors:
- Muscarinic (M1)
- Dopamine (D2)
- Histamine (H1)
- Serotonin (5-HT3)
- Neurokinin (NK-1)
- 5-HT3, D2, and NK-1 antagonists used to treat chemotherapy-induced vomiting.
- M1 and H1 antagonists used to treat motion sickness and hyperemesis gravidarum.
Sleep Physiology
- Sleep cycle is regulated by the circadian rhythm, which is driven by Suprachiasmatic Nucleus (SCN) of hypothalamus.
- Circadian rhythm controls nocturnal release of ACTH, Prolactin, Melatonin, Norepinephrine: SCN → Norepinephrine release → Pineal Gland → Melatonin
- SCN is regulated by environment (eg. light).
- Two Stages:
- Rapid-Eye Movement (REM)
- Non-REM
- Alcohol, benzodiazepines, and barbiturates are associated with ↓ REM sleep and delta wave sleep.
- Norepinephrine also ↓ REM sleep.
- Benzodiazepines are useful for night terrors and sleepwalking by ↓ N3 and REM sleep.
Sleep Physiology
Neuroanatomy:
major relay for all ascending sensory information except olfaction
Thalamus
Thalamus:
- Input:
- spinothalamic and dorsal columns/medial lemniscus
- Senses:
- vibration
- pain
- pressure
- proprioception
- light touch
- temperature
- Destination:
- 1° Somatosensory Cortex
Ventral PosteroLateral Nucleus
- Senses:
- Vibration
- Pain
- Pressure
- Proprioception
- Light Touch
- Temperature
Thalamus:
- Input:
- trigeminal and gustatory pathway
- Senses:
- face sensation
- taste
- Destination:
- 1° Somatosensory Cortex
Ventral PosteroMedial Nucleus
Makeup goes on the face.
Thalamus:
- Input:
- CN II
- optic chiasm
- optic tract
- Senses:
- vision
- Destination:
- Calcarine Sulcus
Lateral Geniculate Nucleus
Lateral = Light
Thalamus:
- Input:
- superior olive and inferior colliculus of tectum optic chiasm
- Senses:
- hearing
- Destination:
- Auditory Cortex of Temporal Lobe
Medial Geniculate Nucleus
Medial = Music
Thalamus:
- Input:
- basal ganglia
- cerebellum
- Senses:
- motor
- Destination:
- Motor Cortex
Ventral Lateral Nucleus
Neuroanatomy:
- collection of neural structures involved in emotion, long-term memory, olfaction, behavior modulation, and ANS function
- Consists of:
- Hippocampus
- Amygdalae
- Mammillary Bodies
- Anterior Thalamic Nuclei
- Cingulate Gyrus
- Entorhinal Cortex
- Responsible for:
- feeding
- fleeing
- fighting
- feeling
- sex
Limbic System
5 F’s:
- Feeding
- Fleeing
- Fighting
- Feeling
- Fucking
Dopaminergic Pathways:
- ↓ activity → “negative” symptoms (eg. anergia, apathy, lack of spontaneity)
- antipsychotic drugs have limited effect
Mesocortical
Dopaminergic Pathways:
- ↑ activity → “positive” symptoms (eg. delusions, hallucinations)
- 1° therapeutic target of antipsychotic drugs → ↓ positive symptoms (eg. in schizophrenia)
Mesolimbic
Dopaminergic Pathways:
- ↓ activity → extrapyramidal symptoms (eg. dystonia, akathisia, parkinsonism, tardive dyskinesia)
- major dopaminergic pathway in brain
- significantly affected by movement disorders and antipsychotic drugs
Nigrostriatal
Dopaminergic Pathways:
↓ activity → ↑ prolactin → ↓ libido, sexual
dysfunction, galactorrhea, gynecomastia (in
men).
Tuberoinfundibular
Cerebellum Input
- Contralateral Cortex via Middle Cerebellar Peduncle
- ipsilateral proprioceptive information via Inferior Cerebellar Peduncle from spinal cord
Cerebellum Output:
- Purkinje Cells (always inhibitory) → Deep Nuclei of Cerebellum → Contralateral Cortex via Superior Cerebellar Peduncle
- Deep Nuclei (lateral → medial)
- Dentate
- Emboliform
- Globose
- Fastigial
Don’t Eat Greasy Foods.
Neuroanatomy:
- important in voluntary movements and making postural adjustments
- receives cortical input, provides negative feedback to cortex to modulate movement
Basal Ganglia
- *D1-R**eceptor = D1Rect Pathway
- *I**ndirect (D2) = Inhibitory
Basal Ganglia:
Putamen (motor) + Caudate (cognitive)
Striatum
Basal Ganglia:
Putamen + Globus Pallidus
Lentiform
Cerebral Cortex Regions
Homunculus
- Topographic representation of motor (shown) and sensory areas in the cerebral cortex.
- Distorted appearance is due to certain body regions being more richly innervated and thus having ↑ cortical representation.
Cerebral Perfusion
- Brain perfusion relies on tight autoregulation.
- Cerebral perfusion is primarily driven by
- Pco2 (Po2 also modulates perfusion in severe
- hypoxia).
- Cerebral perfusion relies on a pressure gradient between mean arterial pressure (MAP) and ICP.
- ↓ blood pressure or ↑ ICP → ↓ cerebral perfusion pressure (CPP)
- therapeutic hyperventilation → ↓ Pco2 → vasoconstriction → ↓ cerebral blood flow → ↓ intracranial pressure (ICP)
- May be used to treat acute cerebral edema (eg. 2° to stroke) unresponsive to other interventions.
- CPP = MAP – ICP
- If CPP = 0, there is no cerebral perfusion → brain death.
- Hypoxemia increases CPP only if Po2 < 50 mm Hg.
- CPP is directly proportional to Pco2 until Pco2 > 90 mm Hg.
Cerebral Arteries—Cortical Distribution
Watershed Zones
- Between anterior cerebral/middle cerebral, posterior cerebral/middle cerebral arteries (cortical border zones); or may also occur between the superficial and deep vascular territories of the middle cerebral artery (internal border zones).
- Damage by severe hypotension → proximal upper and lower extremity weakness (if internal border zone stroke), higher order visual dysfunction (if posterior cerebral/middle cerebral cortical border zone stroke).
Circle of Willis
System of anastomoses between anterior and posterior blood supplies to brain.
Neuropathology:
- presents with signs/symptoms of ↑ ICP (eg. headache, seizures, focal neurologic deficits)
- may lead to venous hemorrhage
- associated with hypercoagulable states (eg. pregnancy, OCP use, factor V Leiden)
Venous Sinus Thrombosis
Ventricular System
- Lateral Ventricles → 3rd Ventricle via right and left Interventricular Foramina of Monro
- 3rd ventricle → 4th ventricle via Cerebral Aqueduct of Sylvius
- 4th ventricle → subarachnoid space via:
- Foramina of Luschka = Lateral
- Foramen of Magendie = Medial
- CSF made by ependymal cells of choroid plexus.
- Travels to subarachnoid space via foramina of Luschka and Magendie, is reabsorbed by arachnoid granulations, and then drains into dural venous sinuses.
Brain Stem—Ventral View
- 4 CN are above pons (I, II, III, IV)
- 4 CN exit the pons (V, VI, VII, VIII)
- 4 CN are in medulla (IX, X, XI, XII)
- 4 CN nuclei are medial (III, IV, VI, XII)
- “Factors of 12, except 1 and 2.”
Brain Stem—Dorsal View
(cerebellum removed)
- Pineal Gland
- melatonin secretion, circadian rhythms
- Superior Colliculi
- direct eye movements to stimuli (noise/movements) or objects of interest
- Inferior Colliculi
- auditory
- Your eyes are above your ears, and the superior colliculus (visual) is above the inferior colliculus (auditory).
Cranial Nerve Nuclei
- Located in tegmentum portion of brain stem (between dorsal and ventral portions):
- Midbrain—nuclei of CN III, IV
- Pons—nuclei of CN V, VI, VII, VIII
- Medulla—nuclei of CN IX, X, XII
- Spinal cord—nucleus of CN XI
- Lateral Nuclei = sensory (aLar plate)
- Medial Nuclei = Motor (basal plate)
- Sulcus Limitans—separates the cranial nerve motor nuclei from the sensory nuclei
Cranial Nerve and Vessel Pathways
Cranial Nerves:
- eye movement (SO)
- motor
Trochlear IV
Cranial Nerves:
- mastication
- facial sensation (ophthalmic, maxillary, mandibular divisions)
- somatosensation from anterior 2/3 of tongue
- both sensory and motor
Trigeminal V
Cranial Nerves:
- facial movement
- taste from anterior 2/3 of tongue (chorda tympani)
- lacrimation
- salivation (submandibular and sublingual glands)
- eyelid closing (orbicularis oculi)
- auditory volume modulation (stapedius)
- both sensory and motor
Facial VII
Cranial Nerves:
- taste and sensation from posterior 1/3 of tongue
- swallowing
- salivation (parotid gland)
- monitoring carotid body and sinus chemo- and baroreceptors
- elevation of pharynx/larynx (stylopharyngeus)
- both sensory and motor
Glossopharyngeal IX
Cranial Nerves:
- taste from supraglottic region
- swallowing
- soft palate elevation
- midline uvula
- talking
- cough reflex
- parasympathetics to thoracoabdominal viscera
- monitoring aortic arch chemo- and baroreceptors
- both sensory and motor
Vagus X
Vagal Nuclei:
- visceral sensory information (eg. taste, baroreceptors, gut distention)
- CN VII, IX, X
Nucleus Solitarius
Solitarius = Sensory
Vagal Nuclei:
- motor innervation of pharynx, larynx, and upper esophagus (eg, swallowing, palate elevation)
- CN IX, X, XI (cranial portion)
Nucleus Ambiguus
AMbiguus = Motor
Vagal Nuclei:
- sends autonomic (parasympathetic) fibers to heart, lungs, and upper GI
- CN X
Dorsal Motor Nucleus
Cranial Nerve Reflexes:
- Afferent:
- V1 ophthalmic (nasociliary branch)
- Efferent:
- bilateral VII (temporal branch: orbicularis oculi)
Corneal
Cranial Nerve Reflexes:
- Afferent:
- V1 (loss of reflex does not preclude emotional tears)
- Efferent:
- VII
Lacrimation
Cranial Nerve Reflexes:
- Afferent:
- V3 (sensory—muscle spindle from masseter)
- Efferent:
- V3 (motor—masseter)
Jaw Jerk
Cranial Nerve Reflexes:
- Afferent:
- II
- Efferent:
- III
Pupillary
Cranial Nerve Reflexes:
- Afferent:
- IX
- Efferent:
- X
Gag
Mastication Muscles
- 3 muscles close the jaw:
- Masseter
- TeMporalis
- Medial Pterygoid
M’s Munch
- 1 muscle opens the jaw:
- Lateral Pterygoid
Lateral Lowers (when speaking of pterygoids with respect to jaw motion)
- All are innervated by trigeminal nerve (V3).
- “It takes more muscle to keep your mouth shut.”
Spinal Nerves
- There are 31 pairs of spinal nerves in total:
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
- Nerves C1–C7 exit above the corresponding vertebra. C8 spinal nerve exits below C7 and above T1.
- All other nerves exit below (eg. C3 exits above the 3rd cervical vertebra; L2 exits below the 2nd lumbar vertebra).
Neuropathology:
- nucleus pulposus (soft central disc) herniates through annulus fibrosus (outer ring)
- usually occurs posterolaterally at L4–L5 or L5–S1
- nerve usually affected is below the level of herniation (eg. L3–L4 disc spares L3 nerve and involves L4 nerve)
- compression of S1 nerve root → absent ankle reflex
Vertebral Disc Herniation
Spinal Cord—Lower Extent
- In adults, spinal cord ends at lower border of L1–L2 vertebrae.
- Subarachnoid Space (which contains the CSF) extends to lower border of S2 vertebra.
- Lumbar puncture is usually performed between L3–L4 or L4–L5 (level of cauda equina).
- “To keep the cord alive, keep the spinal needle between L3 and L5.”
- Goal of lumbar puncture is to obtain sample of CSF without damaging spinal cord.
Spinal Cord and Associated Tracts
- Legs (Lumbosacral) are Lateral in Lateral corticospinal, spinothalamic tracts.
- Dorsal columns are organized as you are, with hands at sides.
- “Arms outside, legs inside.”
_____ tracts synapse and then cross.
Ascending
Clinical Reflexes
Reflexes count up in order (main nerve root in bold):
- Achilles reflex = S1, S2 (“buckle my shoe”)
- Patellar reflex = L3, L4 (“kick the door”)
- Biceps and Brachioradialis reflexes = C5, C6 (“pick up sticks”)
- Triceps reflex = C7, C8 (“lay them straight”)
Additional reflexes:
- Cremasteric reflex = L1, L2 (“testicles move”)
- Anal Wink reflex = S3, S4 (“winks galore”)
Primitive Reflexes
- CNS reflexes that are present in a healthy infant, but are absent in a neurologically intact adult.
- Normally disappear within 1st year of life.
- These “primitive” reflexes are inhibited by a mature/developing frontal lobe.
- They may reemerge in adults following frontal lobe lesions → loss of inhibition of these reflexes.
Primitive Reflexes:
- “hang on for life”
- abduct/extend arms when startled, and then draw together
Moro Reflex
Primitive Reflexes:
- dorsiflexion of large toe and fanning of other toes with plantar stimulation
- Babinski Sign—presence of this reflex in an adult, which may signify a UMN lesion
Plantar Reflex
Primitive Reflexes:
stroking along one side of the spine while newborn is in ventral suspension (face down) causes lateral flexion of lower body toward stimulated side
Galant Reflex
Landmark Dermatomes:
posterior half of skull
C2
Landmark Dermatomes:
- high turtleneck shirt
- diaphragm and gallbladder pain referred to the right shoulder via phrenic nerve
C3
C3, 4, 5 keeps the diaphragm alive.
Landmark Dermatomes:
low-collar shirt
C4
Landmark Dermatomes:
includes thumbs
C6
Thumbs up sign on left hand looks like a 6.
Landmark Dermatomes:
at the nipple
T4
T4 at the teat pore.
Landmark Dermatomes:
at the xiphoid process
T7
Landmark Dermatomes:
- at the umbilicus
- important point of referred pain in early appendicitis
T10
belly butten
Landmark Dermatomes:
at the inguinal ligament
L1
Inguinal Ligament
Landmark Dermatomes:
includes the kneecaps
L4
down on ALL 4’s
Landmark Dermatomes:
sensation of penile and anal zones
S2, S3, S4
S2, 3, 4 keep the penis off the floor
Common Brain Lesions:
- disinhibition and deficits in concentration, orientation, and judgment
- may have reemergence of primitive reflexes
Frontal Lobe
Common Brain Lesions:
- eyes look toward (destructive) side of lesion
- in seizures (irritative), eyes look away from side of the lesion
Frontal Eye Fields
Common Brain Lesions:
- eyes look away from side of lesion
- ipsilateral gaze palsy (inability to look toward side of lesion)
Paramedian Pontine Reticular Formation
Common Brain Lesions:
- internuclear ophthalmoplegia (impaired adduction of ipsilateral eye; nystagmus of contralateral eye with abduction)
- Multiple Sclerosis
Medial Longitudinal Fasciculus
Common Brain Lesions:
- agraphia, acalculia, finger agnosia, left-right disorientation
- Gerstmann Syndrome
Dominant Parietal Cortex
Common Brain Lesions:
- agnosia of the contralateral side of the world
- Hemispatial Neglect Syndrome
Nondominant Parietal Cortex
Common Brain Lesions:
Anterograde Amnesia—inability to make new memories
Hippocampus (bilateral)
Common Brain Lesions:
- may result in tremor at rest, chorea, and athetosis
- Parkinson Disease
- Huntington Disease
Basal Ganglia
Common Brain Lesions:
contralateral hemiballismus
Subthalamic Nucleus
Common Brain Lesions:
Wernicke-Korsakoff Syndrome
- confusion
- ataxia
- nystagmus
- ophthalmoplegia
- memory loss (anterograde and retrograde amnesia)
- confabulation
- personality changes
Mammillary Bodies (bilateral)
Wernicke problems come in a CAN O’ beer.
- Confusion
- Ataxia
- Nystagmus
- Ophthalmoplegia
Common Brain Lesions:
- Klüver-Bucy Syndrome
- disinhibited behavior
- hyperphagia
- hypersexuality
- hyperorality
- disinhibited behavior
- HSV-1 Encephalitis
Amygdala (bilateral)
Common Brain Lesions:
- Parinaud Syndrome
- vertical gaze palsy
- pupillary light-near dissociation
- lid retraction
- convergence-retraction nystagmus
- stroke, hydrocephalus, pinealoma
Dorsal Midbrain
Common Brain Lesions:
reduced levels of arousal and wakefulness (eg. coma)
Reticular Activating System (midbrain)
Common Brain Lesions:
- intention tremor, limb ataxia, loss of balance
- ipsilateral deficits
- fall toward side of lesion
Cerebellar Hemisphere
Cerebellar hemispheres are laterally located—affect lateral limbs.
Common Brain Lesions:
- Decorticate (flexor) Posturing
- lesion above
- presents with flexion of upper extremities and extension of lower extremities
- Decerebrate (extensor) Posturing
- lesion at or below
- presents with extension of upper and lower extremities
- worse prognosis
Red Nucleus
Common Brain Lesions:
- truncal ataxia (wide-based, “drunken sailor” gait), dysarthria
- degeneration associated with chronic alcohol use
Cerebellar Vermis
Vermis is centrally located—affects central body.
Ischemic Brain Disease/Stroke
- Irreversible damage begins after 5 minutes of hypoxia.
- Most vulnerable: hippocampus, neocortex, cerebellum (Purkinje cells), watershed areas. Irreversible neuronal injury.
- Hippocampus is most vulnerable to ischemic hypoxia (“vulnerable hippos”).
- Stroke Imaging:
- CT Scan
- Noncontrast CT to exclude hemorrhage (before tPA can be given)
- CT detects ischemic changes in 6–24 hr
- MRI
- Diffusion-Weighted MRI can detect ischemia within 3–30 min
- CT Scan
Histologic Features of Stroke:
12-24 hours
eosinophilic cytoplasm + pyknotic nuclei (red neurons)
Histologic Features of Stroke:
24-72 hours
necrosis + neutrophils
Histologic Features of Stroke:
3-5 days
macrophages (microglia)
Histologic Features of Stroke:
1-2 weeks
reactive gliosis (astrocytes + vascular proliferation
Histologic Features of Stroke:
> 2 weeks
glial scar
Neuropathology:
acute blockage of vessels → disruption of blood flow and subsequent ischemia → liquefactive necrosis
Ischemic Stroke
Ischemic Stroke:
- due to hypoperfusion or hypoxemia
- common during cardiovascular surgeries
- tends to affect watershed areas
Hypoxic
Ischemic Stroke:
Treatment
- tPA (if within 3–4.5 hr of onset and no hemorrhage/risk of hemorrhage).
- Reduce risk with medical therapy (eg. Aspirin, Clopidogrel); optimum control of blood pressure, blood sugars, lipids; and treat conditions that ↑ risk (eg. atrial fibrillation, carotid artery stenosis).
Neuropathology:
- brief, reversible episode of focal neurologic dysfunction without acute infarction (⊝ MRI), with the majority resolving in < 15 minutes
- deficits due to focal ischemia
Transient Ischemic Attack
Neuropathology:
- bleeding into ventricles
- increased risk in premature and low-birth-weight infants
- originates in germinal matrix, a highly vascularized layer within the subventricular zone
- due to reduced glial fiber support and impaired autoregulation of BP in premature infants
- can present with altered level of consciousness, bulging fontanelle, hypotension, seizures, and coma
Neonatal Intraventricular Hemorrhage
Intracranial Hemorrhage:
- rupture of middle meningeal artery (branch of maxillary artery), often 2° to skull fracture (circle in A) involving the pterion (thinnest area of the lateral skull)
- lucid interval
- scalp hematoma (arrows in A) and rapid intracranial expansion (arrows in B) under systemic arterial pressure → transtentorial herniation, CN III palsy
- CT shows biconvex (lentiform), hyperdense blood collection (B) not crossing suture lines
Epidural Hematoma
Intracranial Hemorrhage:
- rupture of bridging veins
- can be acute (traumatic, high-energy impact → hyperdense on CT) or chronic (associated with mild trauma, cerebral atrophy, elderly, alcoholism → hypodense on CT)
- also seen in shaken babies
- Predisposing Factors:
- brain atrophy
- trauma
- crescent-shaped hemorrhage (red arrows in C and D) that crosses suture lines
- can cause midline shift (yellow arrow in C)
- findings of “acute on chronic” hemorrhage (blue arrows in D)
Subdural Hematoma
Intracranial Hemorrhage:
- bleeding (E, F) due to trauma, or rupture of an aneurysm (such as a saccular aneurysm E) or arteriovenous malformation
- rapid time course
- patients complain of “worst headache of my life”
- bloody or yellow (xanthochromic) spinal tap
- vasospasm can occur due to blood breakdown or rebleed 3–10 days after hemorrhage → ischemic infarct
- Nimodipine is used to prevent/reduce vasospasm
- ↑ risk of developing communicating and/or obstructive hydrocephalus
Subarachnoid Hemorrhage
Intracranial Hemorrhage:
- most commonly caused by systemic hypertension
- also seen with amyloid angiopathy (recurrent lobar hemorrhagic stroke in elderly), vasculitis, and neoplasm
- may be 2º to reperfusion injury in ischemic stroke
- hypertensive hemorrhages (Charcot-Bouchard microaneurysm) most often occur in the putamen of the basal ganglia (lenticulostriate vessels G), followed by thalamus, pons, and cerebellum (H)
Intraparenchymal Hemorrhage
Effects of Strokes:
Anterior Circulation
Effects of Strokes:
Posterior Circulation