Neurology Flashcards
Notochord induces overlying ectoderm to
Notochord induces overlying ectoderm to differentiate into neuroectoderm and form neural plate
Neural plate gives rise to
Neural plate gives rise to neural tube and neural crest cells
Notochord becomes
Notochord becomes nucleus pulposus of intervetebral disc in adults
Prosencephalon gives rise to
Telencephalon and diencephalon
Mesencephalon (of the 3 primary vesicles) gives rise to
Mesencephalon
Rhombencephalon gives rise to
Metencephalon and myelencephalon
Telencephalon gives rise to
Cerebral hemispheres and lateral ventricles
Diencephalon gives rise to
Thalamus, hypothalamus, and third ventricle
Mesencephalon gives rise to
Midbrain and aqueduct
Metencephalon gives rise to
Pon, cerebellum, and upper part of 4th ventricle
Myelencephalon gives rise to
Medulla and lower part of 4th ventricle
Neuroectoderm
- CNS neurons
- Ependymal cells (inner lining of ventricles, make CSF)
- Oligodendroglia
- Astrocytes
Neural crest
- PNS neurons
- Schwann cells
Mesoderm
Microglia
When do neuropores normally fuse
4th week
Confirmatory test for neural tube defect after AFP
↑ acetylcholinesterase (AChE) in amniotic fluid
Anencephaly
- Malformation of anterior neural tube → no forebrain, open calvarium
- Clinical findings: ↑ AFP, polyhydramnios (no swallowing center in brain)
- Associated with maternal type 1 diabetes
- Maternal folate supplementation ↓ risk
Holoprosencephaly
- Failure of right and left 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 Patau syndrome and fetal alcohol syndrome
Anencephaly is associated with
Maternal type 1 diabetes
Holoprosencephaly is associated with
Patau syndrome and fetal alcohol syndrome
Chiari II malformation
- Herniation of low-lying cerebellar vermis through foramen magnum with aqueductal stenosis → hydrocephalus
- Usually associated with lumbosacral meningomyelocele (paralysis/sensory loss at and below the level of the lesion)
Dandy-Walker syndrome
- Agenesis of cerebellar vermis with cystic enlargement of 4th ventricle (fills the enlarged posterior fossa)
- Associated with noncommunicating hydrocephalus, spina bifida
Chiari I malformation
- Cerebellar tonsillar ectopia > 3-5 mm
- Congenital, usually asymptomatic in childhood, manifest with headaches and cerebellar symptoms
- Associated with syringomyelia
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 the tongue), genioglossus (protrudes 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
What forms multinucleated giant cells in the CNS of HIV infected patients
HIV-infected microglia fuse to form multinucleated giant cells in the CNS
How does myelin change the space constant, conduction velocity and time constant
- ↑ space constant
- ↑ conduction velocity
- ↓ time constant
What is the embryologic derivation of Schwann cells and oligodendrocytes
Oligodendrocytes → neuroectoderm
Schwann cells → neural crest
Oligodendroglia are injured in what disease processes
- MS
- Progressive multifocal leukoencephalopathy (PML)
- Leukodystrophies
Free nerve endings
- C → slow, unmyelinated fibers
- A-delta → fast, myelinated fibers
- All skin, epidermis, some viscera
- Pain, temperature
Meissner corpuscles
- Large, myelinated fibers; adapt quickly
- Glabrous (hairless) skin
- Dynamic, fine/light tough, position sense
Pacinian corpuscles
- Large myelinated fibers; adapt quickly
- Deep skin layers, ligaments, joints
- Vibration, pressure
Merkel discs
- Large, myelinated fibers; adapt slowly
- Finger tips, superficial skin
- Pressure, deep static touch (eg shapes, edges)
Ruffini corpuscles
- Dendritic endings with capsule; adapt slowly
- Fingertips, joints
- Pressure, slippage of objects along surface of skin, joint angle change
What must be rejoined in microsurgery for limb reattachment
Perineurium
Epineurium
Dense connective tissue that surrounds entire nerve (fascicles and BLOOD VESSELS)
Location of acetylcholine synthesis
Basal nucleus of Meynert
Location of dopamine synthesis
Ventral tegmentum, SNpc
Location of GABA synthesis
Nucleus accumbens
Location of norepinephrine synthesis
Locus ceruleus
Location of serotonin synthesis
Raphe nucleus
Neurotransmitters in anxiety
- ↓ GABA
- ↑ norepinephrine
- ↓ serotonin
Neurotransmitters in depression
- ↓ dopamine
- ↓ norepinephrine
- ↓ serotonin
Neurotransmitters in schizophrenia
↑ dopamine
Neurotransmitters in Alzheimer disease
- ↓ acetylcholine
- ↑ glutamate
Neurotransmitters in Huntington disease
- ↓ acetylcholine
- ↑ dopamine
- ↓ GABA
Neurotransmitters in Parkinson disease
- ↑ acetylcholine
- ↓ dopamine
- ↑ serotonin
Blood-brain barrier formed by what 3 structures
- Tight junctions between nonfenestrated capillary endothelial cells
- Basement membrane
- Astrocyte foot processes
How do glucose and amino acids cross the BBB
Slowly by carrier mediated transport mechanisms
What kinds of substances cross the BBB rapidly via diffusion
Nonpolar/ lipid-soluble substances
Vasogenic edema
Infarction and/or neoplasm destroys endothelial cell tight junctions causing vasogenic edema
What is the hypothalamus responsible for
- Thirst and water balance
- Adenohypophysis control (regulates anterior pituitary)
- Neurohypophysis releases hormones hormones produced in the hypothalamus
- Hunger
- Autonomic regulation
- Temperature regulation
- Sexual urges
“TAN HATS”
What are input areas of the hypothalamus
- Organum vasculosum of the lamina terminalis (OVLT) → senses changes in osmolarity
- Area postrema (found in medulla) → responds to emetics
Lateral area of hypothalamus
- Hunger
- Destruction → anorexia, failure to thrive (infants)
- Stimulated by ghrelin
- Inhibited by leptin
Ventromedial area of hypothalamus
- Satiety
- Destruction (eg craniopharyngioma) → hyperphagia
- Stimulated by leptin
Anterior hypothalamus
- Cooling
- Parasympathetic
Posterior hypothalamus
- Heating
- Sympathetic
Suprachiasmatic nucleus
Circadian rhythm
Sleep physiology
- Circadian rhythm controls nocturnal release of ACTH, prolactin, melatonin, norepinephrine
- SCN → norepinephrine release → pineal gland → melatonin
- SCN is regulated by environment
Extraocular movements during REM sleep are due to
Activity of PPRF (paramedian pontine reticular formation/ conjugate gaze center)
Increase in what neurotransmitter occurs during REM sleep
Acetylcholine
What drugs are associated with ↓ REM sleep
- Alcohol, benzodiazepines, and barbiturates → ↓ REM sleep, ↓ delta wave sleep
- Norepinephrine → ↓ REM sleep
In which stage of sleep do bruxisms occur
N2
In what stage of sleep do night terrors, sleepwalking and bedwetting occur
N3
Ventral posterolateral nucleus of thalamus
- Input from spinothalamic and dorsal columns/medial lemniscus
- Senses pain, temperature, touch, vibration and propioception
- Destination is primary somatosensory cortex
Ventral posteromedial nucleus of thalamus
- Input from trigeminal and gustatory pathway
- Senses face sensation and taste
- Destination is primary somatosensory cortex
“Makeup goes of the face”
Lateral geniculate nucleus of thalamus
- Input from CN II
- Vision
- Destination is calacrine sulcus
“Lateral = light”
Medial geniculate nucleus of thalamus
- Input from superior olive and inferior colliculus of tectum
- Hearing
- Destination is auditory cortex of temporal lobe
“Medial = music”
Ventral lateral nucleus of thalamus
- Input from basal ganglia and cerebellum
- Motor
- Destination is motor cortex
Limbic system
- Collection of neural structures involved in emotion, long-term memory, olfaction, behavior modification, ANS function
- Structures include hippocampus, amygdala, fornix, mammillary bodies, cingulate gyrus
- Responsible for “Feeding, Fleeing, Fighting, Feeling and Fucking”
Dopaminergic pathways
- Mesocortical
- Mesolimbic
- Nigrostriatal
- Tuberoinfundibular
Mesocortical dopaminergic pathway
- ↓ activity → “negative” symptoms (eg flat affect, limited speech)
- Antipsychotic drugs have limited effect
Mesolimbic dopaminergic pathway
- ↑ activity → “positive” symptoms (eg delusions, hallucinations)
- Primary therapeutic target of antipsychotic drugs → ↓ positive symptoms (eg schizophrenia)
Nigrostriatal dopaminergic pathway
- ↓ activity → extrapyramidal symptoms (eg dystonia, akathisia, parkinsonism, tardive dyskinesia)
- Major dopaminergic pathway in brain
- Significantly affected by movement disorders
Tuberoinfundibular dopaminergic pathway
- ↓ activity → ↑ prolacting → ↓ libido, sexual dysfunction, galactorrhea, gynecomastia (in men)
Input to cerebellum
- Contralateral cortex via middle cerebellar peduncle
- Ipsilateral propioceptive information via inferior cerebellar peduncle from spinal cord
Output from cerebellum
- Sends information to contralateral cortex to modulate movement
- Output nerves: Purkinje cells → deep nuclei of cerebellum → contralateral cortex via superior cerebellar peduncle
- Deep nuclei (lateral to medial): dentate → emboliform → globose → fastigial (“Don’t Eat Greasy Foods”)
Lateral lesions to cerebellum
- Affect voluntary movement of extremities
- When injured, propensity to fall toward injured (ipsilateral) side
Medial lesions to cerebellum
- Involvement of midline structures (vermal cortex, fastigial nuclei) and/or flocculonodular lobe → truncal ataxia (wide based cerebelar gait), nystagmus, head tilting
- Generally result in bilateral motor deficits affecting axial and proximal limb musculature
Excitatory pathway
Cortical inputs stimulate the striatum, stimulating the release of GABA, which inhibits GABA release from the GPi, disinhibiting the thalamus via the GPi (↑ motion)
Inhibitory pathway
Cortical inputs stimulate the striatum, releasing GABA that disinhibits STN via GPe inhibition and STN stimulates GPi to inhibit the thalamus (↓ motion)
Compare D1 and D2
D1 → stimulates the excitatory pathway
D2 → inhibiting the inhibitory pathway (↑ motion)
Athetosis
- Slow, writing movements; especially seen in fingers
- Lesion of basal ganglia (eg Huntington)
Chorea
- Sudden, jerky, purposeless movements
- Lesion of basal ganglia (eg Huntington)
Dystonia
- Sustained, involuntary muscle contractions
- Writer’s cramp; blepharospasm (sustained eyelid twitch)
Essential tremor
- High-frequency tremor with sustained posture (eg outstretched arms)
- Worsened with movement or when anxious
- Often familial
- Patients often self-medicate with alcohol, which ↓ tremor amplitude
- Treatment: nonselective β blockers (eg propanolol), primidone
Hemiballismus
- Sudden, wild flailing of 1 arm +/- ipsilateral leg
- Lesion to CONTRALATERAL subthalamic nucleus (eg lacunar stroke)
Intention tremor
- Slow, zigzag motion when pointing/extending toward a target
- Cerebellar dysfunction
Myoclonus
- Sudden, brief, uncontrolled muscle contraction
- Jerks
- Hiccups
- Common in metabolic abnormalities such as renal or liver failure
Resting tremor
- Uncontrolled movement of distal appendages (most noticeable in hands)
- Tremor alleviated by intentional movement
- Parkinson disease (“pill-rolling tremor”)
How to treat essential tremor
Nonselective β blockers (eg propanolol) or primidone
How does neuronal death occur in Huntington disease
Neuronal death via NMDA-R binding and glutamate excitotoxicity
Compare aphasia and dysarthria
Aphasia → higher-order language deficit (inability to understand/ speak/ read/ write)
Dysarthria → motor inability to speak (movement deficit)
Conduction apahsia
- Fluent speech
- Intact comprehension
- Impaired repetition
- Can be caused by damage to arcuate fasciculus
Global aphasia
- Nonfluent speech
- Impaired comprehension
- Impaired repetition
- Damage to arcuate fasciculus, Broca and Wernicke area
Transcortical motor aphasia
- Nonfluent speech
- Intact comprehension
- Intact repetition
- Affects frontal lobe around Broca area, but Broca area is spared
Transcortical sensory aphasia
- Fluent speech
- Impaired comprehension
- Intact repetition
- Affects temporal lobe around Wernicke area, but Wernicke area is spared
Transcortical aphasia, mixed
- Nonfluent speech
- Impaired comprehension
- Intact repitition
- Broca and Wernicke area and arcuate fasciculus remain intact
- Surrounding watershed areas affected
Lesion to amygdala (bilateral)
- Kluver-Bucy syndrome → disinhibited behavior (eg hyperphagia, hypersexuality, hyperorality)
- Associated with HSV1 encephalitis
Lesion to frontal lobe
- Disinhibition and deficits in concentration, orientation, judgement
- May have reemergence of primitive reflexes
Lesion to nondominant parietal cortex
Hemispatial neglect syndrome (agnosia of the contralateral side of the world)
Lesion to dominant parietal cortex
- Agraphia
- Acalculia
- Finger agnosia
- Left-right disorientation
- Gerstmann syndrome → ability to read and speak is intact, results from damage to visual association cortex (located in angular gyrus)
Lesion to reticular activating system (midbrain)
Reduced levels of arousal and wakefulness (eg coma)
Lesion to mamillary bodies (bilateral)
- Werncke-Korsakoff syndrome → confusion, ophthalmoplegia, ataxia; memory loss (anterograde > retrograde amnesia), confabulation, personality changes
- Associated with thiamine (B1) deficiency and excessive alcohol use
- Can be precipitated by giving glucose without B1 to a B1 deficient patient
- Wernicke problems come in a CAN of beer → confusion, ataxia, nystagmus
Lesion to basal ganglia
- May result in a tremor at rest, chorea, athetosis
- Parkinson disease
- Huntington disease
Lesion to cerebellar hemisphere
- Intention tremor
- Limb ataxia
- Loss of balance
- Damage to cerebellum → ipsilateral deficits
- Fall toward side of lesion
- Degeneration associated with chronic alcohol use
Lesion to cerebellar vermis
- Truncal ataxia
- Dysarthria
Lesion to subthalamic nucleus
Contralateral hemiballismus
Lesion to hippocampus (bilateral)
Anterograde amnesia → inability to make new memories
Compare lesion to paramedian pontine reticular formation and frontal eye fields
Paramedian pontine reticular formation → eyes look AWAY from side of lesion
Frontal eye fields → eyes look toward lesion
Cerebral perfusion relies on
- Pressure gradient between mean arterial pressure (MAP) and ICP
- ↓ BP or ↑ ICP → ↓ cerebral perfusion pressure (CPP)
- CPP = MAP - ICP
- If CPP = 0, there is no cerebral perfusion → brain death
Therapeutic hyperventilation
↓ pCO2 → vasoconstriction → ↓ cerebral blood flow → ↓ intracranial pressure (ICP)
May be used to treat acute cerebral edema (eg secondary to stroke) unreponsible to other interventions
Middle cerebral artery stroke
Areas of lesions:
- Motor and sensory cortices → upper limb and face
- Temporal lobe → Wernicke area
- Frontal lobe → Broca area
Symptoms:
- Contralateral paralysis and sensory loss → face and upper limb
- Aphasia if in dominant (usually left) hemisphere
- Hemineglect if lesion affects nondominant (usually right) side
Anterior cerebral artery stroke
Areas of lesions:
- Motor and sensory cortices → lower limb
Symptoms:
- Contralateral paralysis and sensory loss → lower limb
Lenticulostriate artery stroke
Areas of lesions:
- Striatum
- Internal capsule
Symptoms:
- Contralateral paralysis and/or sensory loss → face and body
- Absence of cortical signs (eg neglect, aphasia, visual field loss)
Common location of lacunar infarcts, secondary to unmanaged hypertension.
Anterior spinal artery stroke
Areas of lesions:
- Lateral corticospinal tract
- Medial lemniscus
- Caudal medulla → hypoglossal nerve
Symptoms:
- Contralateral paralysis → upper and lower limbs
- ↓ contralateral propioception
- Ipsilateral hypoglossal deviation (tongue deviates ipsilaterally)
MEDIAL MEDULLARY SYNDROME → caused by infarct of paramedian branches of ASA and/or vertebral arteries
Posterior inferior cerebellar artery stroke
Areas of lesions:
- Lateral medulla → vestibular nuclei, lateral spinothalamic tract, spinal trigeminal nucleus, nucleus ambiguus, sympathetic fibers, inferior cerebellar peduncle
Symptoms:
- Vomiting, vertigo, nystagmus
- ↓ pain and temperature sensation from ipsilateral face and contralateral body
- Dysphagia, hoarseness, ↓ gag reflex
- Ipsilateral Horner syndrome
- Ataxia, dymetria
NUCLEUS AMBIGUUS → effects are specific to PICA lesions
LATERAL MEDULLARY (WALLENBERG) SYNDROME
“Don’t pick a (PICA) horse (hoarseness) that can’t eat (dysphagia)”
Anterior inferior cerebellar artery stroke
Areas of lesions:
- Lateral pons → cranial nerve nuclei (vestibular nuclei, facial nerve nucleus, spinal trigeminal nucleus, cochlear nuclei), spinothalamic tract, corticospinal tract, sympathetic fibers
- Middle and inferior cerebellar peduncles
Symptoms:
- Vomiting, vertigo, nystagmus
- Paralysis of face, ↓ lacrimation, salivation, ↓ taste from anterior 2/3 of tongue
- Ipsilateral ↓ pain and temperature of face
- Contralateral ↓ pain and temperature of the body
- Ataxia, dysmetria
LATERAL PONTINE SYNDROME → facial nucleus effects are specific to AICA lesions
“Facial droop means AICA’s pooped”
Basilar artery stroke
Areas of lesions:
- Pons, medulla, lower midbrain, corticospinal and corticobulbar tracts, ocular cranial nerve nuclei, paramedian pointine reticular formation
Symptoms:
- Preserved consciousness, eye movement, blinking
- Quadriplegia, loss of voluntary facial, mouth, and tongue movements
“LOCKED-IN SYNDROME”
Posterior cerebral artery stroke
Areas of lesions:
- Occipital cortex
- Visual cortex
Symptoms:
- Contralateral hemianopia with macular sparing
Charcot-Bouchard microaneurysm
- Common
- Associated with chronic hypertension
- Affects small vessels (eg in basal ganglia, thalamus)
- Not seen on angiogram
Posterior communicating artery saccular aneurysm
- Compression may cause ipsilateral CN III palsy → mydriasis (“blown pupil”)
- May also see ptosis, “down and out” eye
Central post-stroke pain syndrome
- Neuropathic pain due to thalamic lesions
- Initial parasthesias followed in weeks to months by allodynia (ordinarily painless stimuli cause pain) and dysesthesia
- Occurs in 10% of stroke patients
Intraparenchymal hemorrhage
- Most commonly caused by systemic hypertension
- Also seen with amyloid angiopathy (recurrent lobar hemorrhagic stroke in elderly), vasculitis, neoplasm
- May be secondary to reperfusion injury in ischemic stroke
- Typically occurs in basal ganglia and internal capsule (Charcot-Bouchard aneurysm of lenticulostriate vessels), but can be lobar
Areas most vulnerable to ischemia
- Hippocampus
- Neocortex
- Cerebellum
- Watershed areas
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
Venous sinus thrombosis
- Presents with sign/symptoms of ↑ ICP (eg headache, seizures, focal neurologic deficits)
- May lead to venous hemorrhage
- Associated with hypercoaguable states (eg pregnancy, OCP use, factor V Leiden)
Most common locations of vertebral disc herniation
L4-L5 or L5-S1
Where does the spinal cord end
Lower border of L1-L2 vertebrae
Where are lumbar punctures performed
Between L3-L4 or L4-L5
Where does the subarachnoid space end
S2
Dorsal column
- Ascending
- Pressure, vibration, fine touch, and propioception
- 1st order neuron: sensory nerve ending → cell body in DRG → enters spinal cord, ascends ipsilaterally in dorsal column
- Synapse 1: ipsilateral nucleus cuneatus or gracilis (medulla)
- 2nd order neuron: decussates in medulla → ascends contralaterally in medial lemniscus
- Synapse 2: VPL (thalamus)
- 3rd order neuron: sensory cortex
Spinothalamic tract
- Ascending
- Lateral: pain, temperature
- Anterior: crude touch, pressure
- 1st order neuron: sensory nerve ending (A-delta and C fibers) → cell body in DRG → enters spinal cord
- Synapse 1: ipsilateral gray matter (spinal cord)
- 2nd order neuron: decussates at anterior white commissure → ascends contralaterally
- Synapse 2: VPL (thalamus)
- 3rd order neuron: sensory cortex
Lateral corticospinal tract
- Descending
- Voluntary movement of contralateral limbs
- 1st order neuron: UMN: cell body in primary motor cortex → descends ipsilaterally (through internal capsule), most fibers decussate at caudal medulla (pyramidal decussation) → descends contralaterally
- Synapse 1: cell body of anterior horn (spinal cord)
- 2nd order neuron: LMN: leaves spinal cord
- Synapse 2: NMJ
Poliomyelitis and Werdnig-Hoffmann disease
- Congenital degeneration of anterior horns of spinal cord
- LMN lesions only
- “Floppy baby” with marked hypotonia and tongue fasciculation
- Infantile type has median age of death of 7 months
- AR
- Poliomyelitis → asymmetric weakness
- Werdnig-Hoffmann disease → symmetric weakness
Amyotrophic lateral sclerosis
- Combined UMN and LMN deficits with no sensory or bowel/bladder deficits (due to loss of cortical and spinal cord motor neurons, respectively)
- Can be caused by defect in superoxide dismutase 1
- Commonly presents with asymmetric limb weakness (hands/feet), fasciculations, and eventual atrophy
- Treatment: riluzole
Complete occlusion of anterior spinal artery
- Spares dorsal columns and Lissauer tract
- Upper thoracic ASA territory is watershed area, as artery of Adamkiewicz supplies ASA below T8
- Obstruction of artery of Adamkiewicz can also result in an ASA syndrome with urinary and fecal incontinence and impaired motor function of the legs; sensory is often preserved
Tabes dorsalis
- Caused by tertiary syphilis
- Results from degeneration (demyelination) of dorsal columns and roots → progressive sensory ataxia (impaired propioception → poor coordination)
- Associated with Charcot joints, shooting pain, Argyll Robertson pupils
- Exam will demonstrate absence of DTRs and + Rhomberg sign
Syringomyelia
- Syrinx expands and damages anterior white commissure of spinothalamic tract (2nd order neurons) → bilateral loss of pain and temperature sensation in cape like distribution
- Seen with Chiari I malformation
- Can expand and affect other tracts
Vitamin B12 deficiency
- Subacute combined degeneration (SCD) → demyelination of Spinocerebellar tracts, lateral Corticospinal tracts and Dorsal columns
- Ataxic gait, paresthesia, impaired position/vibration sense
Where does poliovirus first replicate
Oropharynx and small intestine before spreading via bloodstream to CNS
Where is poliovirus recovered from
Stool or throat
Friedreich ataxia
- AR trinucleotide repeat (GAA) on chromosome 9 in gene that encodes frataxin (iron binding protein)
- Leads to impairement in mitochondrial functioning
- Degeneration of multiple spinal cord tracts → muscle weakness and loss of DTRs, vibratory sense, propioception
- Staggering gait, frequent falling, nystagmus, dysarthria, pes cavus, hammer toes, diabetes mellitus, hypertrophic cardiomyopathy (cause of death)
- Presents in childhood with kyphoscoliosis
“Friedreich is a fratastic brother: he’s your favorite frat brother, always staggering and falling but has a sweet, big heart”
What is the most common cause of death in patients with Frederich ataxia
Hypertrophic cardiomyopathy
Brown-Sequard syndrome
- Hemisection of spinal cord
- Ipsilateral UMN lesions below the level of lesion (due to corticospinal tract damage)
- Ipsilateral loss of tactile, vibration, propioception sense below level of lesion (due to dorsal column damage → this is because decussation occurs at medulla)
- Contralateral pain and temperature loss below level of lesion (due to spinothalamic tract damage)
- Ipsilateral loss of all sensation at level of lesion
- Ipsilateral LMN signs at level of lesion
- If lesion occurs above T1, patient may present with ipsilateral Horner syndrome due to damage of oculosympathetic pathway
Galant reflex
Stroking along one side of the spine while the newborn is in ventral suspension (face down) causes lateral flexion of lower body toward stimulated side
Parinaud syndrome
Paralysis of conjugate vertical gaze due to lesion in superior colliculi (eg stroke, hydrocephalus, pinealoma)
Nucleus solitarius
- Visceral sensory information (eg taste, baroreceptors, gut distension)
- CN VII, IX, X
Nucleus ambiguus
- Motor innervation of pharynx, larynx, upper esophagus (eg swallowing, elevation)
- CN IX, X, XI (cranial portion)
Dorsal motor nucleus
- Sends autonomic (parasympathetic) fibers to heart, lungs, upper GI
- CN X
CN VII UMN lesion
- Destruction of motor cortex or connection between motor cortex and facial nucleus in pons → contralateral paralysis of lower muscles of facial expression
- Forehead is spared due to its bilateral UMN innervation
CN VII LMN lesion
Destruction of facial nucleus or CN VII anywhere along its course → ipsilateral paralysis of upper and lower muscles of facial expression, hyperacusis, loss of taste sensation to anterior tongue
Facial nerve palsy
- Clinical syndrome of peripheral CN VII (LMN) lesion
- Depending on lesion location and severity, may cause partial or complete loss of function
- When idiopathic (most common), called BELL PALSY
- May also be caused by: Lyme disease, herpes simplex, herpes zoster (Ramsay Hunt syndrome), sarcoidois, tumors, diabetes mellitus
- Treatment is corticosteroids, acyclovir
- Most patients have gradual recovery of function
Cavernous sinus syndrome
- Presents with variable opthalmoplegia, ↓ corneal sensation, Horner syndrome and occasional decreased maxillary sensation
- Secondary to pituitary tumor mass effect, carotid-cavernous fistula, or cavernous sinus thrombosis related to infection
- CN VI is most susceptible to injury
Cholesteatoma
- Overgrowth of desquamated keratin debris within the middle ear space
- May erode ossicles, mastoid air cells → conductive hearing loss
What produces aqueous humor
Produced by nonpigmented epithelium of ciliary body (↓ by β-blockers, α2-agonists, and carbonic anhydrase inhibitors)
Aqueous humor outflow
Trabecular outflow (90%): drainage through trabecular meshwork → canal of Schlemm → episcleral vasculature (↑ with M3 agonist)
Uveoscleral outflow (10%): drainage into uvea and sclera (↑ with prostaglandin agonists)
Open angle glaucoma
- Associated with ↑ age, African-American race, family history
- Painless, more common in US
- PRIMARY → cause unclear
- SECONDARY → blocked trabecular meshwork from WBCs (eg uveitis), RBCs (eg vitreous hemorrhage), retinal elements (eg retinal detachment)
Closed or narrow-angle glaucoma
- PRIMARY → enlargement or forward movement of lens against central iris (pupil margin) → obstruction of normal aqueous flow through pupil → fluid builds up behind iris, pushing peripheral iris against cornea and impeding flow through trabecular meshwork
- SECONDARY → hypoxia from retinal disease (eg diabetes mellitus, vein occlusion) induces vasoproliferation in iris that contracts angle
- CHRONIC CLOSURE → often asymptomatic with damage to optic nerve and peripheral vision
- ACUTE CLOSURE → true emergency; ↑ IOP pushes iris forward → angle closes abruptly; very painful red eye with vision loss, halos around lights, rock-hard eye, frontal headache → DO NOT GIVE EPINEPHRINE B/C OF MYDRIATIC EFFECT
Uveitis
- Inflammation of uvea, specific name based on location within affected eye
- Anterior uveitis → iritis
- Intermediated uveitis → pars planitis (part of ciliary body)
- Posterior uveitis → choriditis and/or retinitis
- May have hypopyon (accumulation of pus in anterior chamber) or conjunctival redness
- Associated with systemic inflammatory disorders (eg sarcoidosis, rheumatoid arthritis, juvenile idiopathic arthritis, HLA-B27 associated conditions)
Age related macular degeneration
- Degeneration of macula (central area of retina)
- Causes distortion (metamorphopsia) and eventual loss of central vision (scotomas)
- DRY (NONEXUDATIVE, > 80%) → deposition of yellowish extracellular material in and between Bruch membrane and retinal pigment epithelium (“drusen”) with gradual ↓ in vision; prevent progression with multivitamin and antioxidant supplements
- WET (EXUDATIVE, 10-15%) → rapid loss of vision due to bleeding secondary to choroidal neovascularization; treat with anti-VEGF (eg ranibizumab)
- Bruch membrane is the innermost layer of the choroid
Diabetic retinopathy
- Retinal damage due to chronic hyperglycemia
- NONPROLIFERATIVE → damaged capillaries leak blood → lipids and fluid seep into retina → hemorrhages and macular edema; treat with blood sugar control
- PROLIFERATIVE → chronic hypoxia results in new blood vessel formation with resultant traction on retina; treat with peripheral retinal photocoagulation, surgery, anti-VEGF
Retinal vein occlusion
- Blockage of central or branch retinal vein due to compression from nearby arterial atherosclerosis
- Retinal hemorrhage and venous engorgement, edema in affected areas
Retinal detachment
- Separation of neurosensory layer of retina (photoreceptor layer with rods and cones) from outermost pigmented epithelium (normally shields excess light, supports retina) → degeneration of photoreceptors → vision loss
- May be secondary to retinal breaks, diabetic traction, inflammatory effusions
- Visualized on fundoscopy as crinkling retinal tissue and changes in vessel direction
- Breaks more common in patients with myopia and/or history of head trauma
- Often preceded by posterior vitreous detachment (flashes and floaters) and eventual monocular loss of vision
Retinitis pigmentosa
- Inherited retinal degeneration
- Painless, progressive vision loss beginning with night blindness (rods affected first)
- Bone spicule shaped deposits around macula
Retinitis
- Retinal edema and necrosis leading to scar
- Often viral (CMV, HSV, VZV) but can be bacterial or parasitic
- May be associated with immunosuppression
Meyer loop
- Inferior retina
- Loops around interior horn of lateral ventricle in the temporal lobe
Dorsal optic radiation
- Superior retina
- Takes the shortest path via internal capsule in the parietal lobe
Charcot triad of MS
- Scanning speech
- Intention tremor (also Incontinence and Internuclear ophthalmoplegia)
- Nystagmus
“SIN”
Treatment for acute inflammatory demyelinating polyradiculopathy
- Respiratory support is critical until recovery
- Plasmapheresis, IV immunoglobulins
- No role for steroids
Acute disseminated (postinfectious) encephalomyelitis
- Mutlifocal periventricular inflammation and demyelination after infection or vaccination
- Presents with rapidly progressive multifocal neurologic symptoms, altered mental status
- Autoimmune disease marked by sudden widespread inflammation of brain and spinal cord, destruction of white matter
Charcot-Marie-Tooth disease
- AKA hereditary motor and sensory neuropathy (HMSN)
- Group of progressive hereditary nerve disorders related to the defective production of protein involved in the structure and function of peripheral nerves or the myelin sheath
- AD
- Assoicated with foot deformities (pes cavus), lower extremity weakness and sensory deficits
Adrenoleukodystrophy
- X linked disorder typically affecting males
- Disrupts metabolism of very-long-chain-fatty acids → excessive buildup in nervous system, adrenal glands, testes
- Progressive disease that can lead to long-term coma/death and adrenal gland crisis
Partial (focal) seizures
- Affect single area of the brain
- Most commonly originate in medial temporal lobe
- Often preceded by seizure aura
- Can secondarily generalize
- TYPES → simple partial, complex partial
- SIMPLE PARTIAL → consciousness intact; motor, sensory, autonomic, psychic
- COMPLEX PARTIAL → impaired consciousness
Generalized seizures
- ABSENCE → petit mal, 3 Hz, no postictal confusion, blank stare
- MYOCLONIC → quick, repetitive jerks
- TONIC-CLONIC → grand mal, alternating stiffening and movement
- TONIC → stiffening
- ATONIC → “drop” seizures (falls to floor); commonly mistaken for fainting
Excruciating periorbital pain with lacrimation and rhinorrhea
Cluster headache
Cluster, tension and migraine localization
- Cluster → unilateral
- Tension → bilateral
- Migraine → unilateral
Peripheral vertigo
- More common
- Inner ear etiology (eg semicircular canal debris, vestibular nerve infection, Meniere disease [low frequency hearing loss])
- Positional testing → DELAYED horizontal nystagmus
Central vertigo
- Brain stem or cerebellar lesion (eg stroke affecting vestibular nuclei or posterior fossa tumor)
- Findings: directional change of nystagmus, skew deviation, diplopia, dysmetria
- Positional testing → IMMEDIATE nystagmus in any direction (may change directions)
- Focal neurologic findings
Encephalotrigeminal angiomatosis
- Sturge-Weber syndrome
- Congenital, non-inherited (somatic) developmental anomaly of neural crest derivatives due to activating mutation of GNAQ gene
- Affects small (capillary-sized) blood vessels → port-wine stain of the face (nevus flammeus, a non-neoplastic “birth mark” in CN V1/V2 distribution)
- Ipsilateral leptomeningeal angioma → seizures/epilepsy
- Intellectual disability
- Episcleral hemangioma → ↑ IOP → early-onset glaucoma
- STURGE-Weber → Sporadic, port-wine Stain, Tram track calcifications (opposing gyri), Unilateral, Retardation, Glaucoma, GNAQ gene, Epilepsy
“Pseudopalisading” pleomorphic tumor cells that border central areas of necrosis and hemorrhage
Glioblastoma multiforme (grade IV astrocytoma)
Can produce EPO and cause secondary polycythemia
Hemangioblastoma → most often cerebellar
Chicken-wire capillary pattern
Oligodendroglioma
Cystic + solid gross appearance
Pilocytic astrocytoma
Can compress 4th ventricle and cause noncommunicating hydrocephalus
Medulloblastoma
Drop metastases to spinal cord
Medulloblastoma
Rod shaped blepharoplasts (basal ciliary bodies) found near nucleus
Ependymoma
Cholesterol crystals found in “motor oil” like fluid within tumor
Craniopharyngioma
β-hCG production
Pinealoma
Pinealoma
- Tumor of pineal gland
- Can cause Parinaud gland (compression of tectum → vertical gaze palsy)
- Obstructive hydrocephalus (compression of cerebral aqueduct)
- Precocious puberty in males (β-hCG production)
- Histologically similar to germ cell tumors (eg testicular seminoma)
Cingulate (subfalcine) herniation under falx cerebri
Can compress anterior cerebral artery
Downward transtentorial (central) herniation
- Caudal displacement of brain stem → rupture of paramedian basilar artery branches → Duret hemorrhages
- Usually fatal
Uncal herniation
- Uncus = medial temporal lobe
- Compresses ipsilateral CN III (blow pupil, “down and out” gaze, ipsilateral PCA (contralateral homonymous hemianopiawith macular sparing), contralateral crus cerebri at the Kernohan notch (ipsilateral paresis; a “false localization sign”)
Cerebellar tonsillar herniation into the foramen magnum
Coma and death results when these herniations compress the brain stem
