Neuro Path Flashcards
Neural Development
- Notochord induces overlying ectoderm to become neuroectoderm. Becomes plates with crest cells, then fold to generate neural tube.
- Notochord remains as NP.
- Alar is sensory and Basal is motor.
Structures of developing Brain
Forebrain: - telencephalon - Hemispheres and lateral ventricles -diencephalon - 3rd ventricle Midbrain: -Mesencephalon - Midbrain, aqueduct Hindbrain (rhombencephalon) -Metencephalon - Cerebellum and pons (4th Ven) -Myelencephalon - Medulla (4th vent)
Neural Tube Defects
- All related to decreased folate at the time of conception.
- All will present with elevated AFP and elvated AchE
- Valproate and carbemazapine may also cause neural tube defects
- SBO: No arch of vertebral body
- Meningocele- Meniges protrude
- Meningomyelocele - Meninges and chord protrude. Leads to paralysis below lesion. Often occompanied by Chiari 2 formation and syringomyelia.
Anencephaly
- Failure of cranial neuropore to close. Folate involved.
- Elevated AFP and polyhydramnios
- Associated with Maternal DM1
Holoprosencephaly
- Failure of separation of cerebral hemispheres.
- Can cause cycloplegia and cleft lip and palate
- Associated with Patau Syndrome
Chiari (II)
- Chiari 1 is often clinically silent. Slight decrease in posterior fossa formation.
- Chiari 2 - Herniation of cerebellar vermis through foramen magnum.
- stenosis of 4th ventricle and noncommunicating hydrocephalus
- Syringomyeleia and Myelomeningocele
- There will often be paralysis below defect
Dandy Walker
- Agenesis of the cerebellar vermis leads to cystic dilation of the 4th ventricle.
- Hydrocephalus
- Associated with spina bifida.
- Presents with vommiting and convulsions secondary to increased ICP
Syringolmyelia
- Cystic dilation of the central canal
- Generally occurs in the thoraco cervical region
- Loss of P/T in capelike distribution, generally involving back and hands. Due to loss of anterior white commisure of crossing spinothalamic fibers.
- Associated with Chiari 1,2 and myelomeningocele
Tongue Development and Sensation and Motor
- Branchial Pouch 1 - Muscles and sensory for CN V3. Makes the anterior 2/3 of tongue and general sensation. Special sensation via chorda tympani (7)
- Branchial Pouch 3 and 4 Make posterior tongue. 3 is done by CN9 and 4 by CN10. CN9 does most taste ans sensation while 10 does the very posterior (nucleus solitarius)
- Foramen cecum (thyroglossal duct) and sulcus terminalis (circumvalate papilla) divide the anterior and psoterior portions of the tongue
- Motor innervation by hypoglossal (12) come from occipital myotomes. Damage will cause deviation towards the side of the lesion (genioglossus unoposed)
Wallerian Degeneration
Destruction of an axon leads to dissolution of distal portion and retraction of the proximal portion.
Chromatolysis
In response to axonal injury the Nissl substance breaks apart and the nucleus is displaced laterally.
Acute ischemic death in neurons
Eosinophilia and an analog of coagulative necrosis with pyknosis and karryorexis.
Diffuse Axonal Injury
- Widespread destruction of white matter in brain. Often leads to vegatative state.
- Shaken baby or TBI
Astrocytes
- Maintain BBB with foot processes, regulate K concentration and assist in NT reycling and clearance.
- Marker is GFAP present in many cancers.
- Reactive gliosis
Microglia
- Mesodermally derived, function as macrophages of CNS
- Site for HIV brain infection, will show large multinucleated cells.
Oligodendrocytes
- Myelinate in CNS, can myelinate many neurons at once.
- Destroyed in MS
- Tumor looks like fried eggs
Schwann Cells
- Neural Crest Derived
- Myelinate in periphery and can aid in regeneration. Myleinate a single neuron at a time.
- Damaged in Guillan Bare
- Schwannomas are characteristic of NF diseases. Bilateraly vestibular in NF2
Sensory Receptors
- Free: A delta (mylinated) C - Pain sensation, present nearly everywhere except minimal in GI
- Meisners Corpuscles: Light touch, enriched on glaborous skin. Rapidly adapting
- Pacinian Corpuscles: Deep Skin: Vibration and pressure
- Merkels Disks: Slowly adapting deep pressure and position
Peripheral Nerve Layers
- Endoneurium surrounds each nerve (location of Guillan Bare Inflammation)
- Perineureum surrounds a fascicle, needs to be rejoined for nerve regeneration
- Epineurium: Strong CT
NE, diesase and Location
- Made in locus cerruleus in pons
- Decreased in depression and increased in anxiety
DA, disease and location
- Increased in psychosis, decreased in parkinsons and depression.
- Ventral tegmentum (midbrain) and SNC
5-HT
- Majority in gut, in brain. Decreased in depression and decreased in anxiety
- Raphe nucleus (pons)
Ach
-decreased in alzheimers and huntingtons. Nucleus of meynert
GABA
- Decreasd in huntingtons and anxiety
- Present in nucleus accumbens
BBB
- Endothelial Cells, BM, Astrocyte foot processes
- Allow lipophilic substances, hydrophilic need transporter (glucose/aa, etc)
- Discontinuous at: Area postrema, osmolar sensors hypothalamus, releasing centers of post pit
- Damage leads to vasogenic edema
Hyropathalmic Nuclei
- Anterior - Cooling body temperature regulation (PANS). Also contains inputs from mamillary body as part of papez circuit.
- Posterior- Heating body temperture (SANS)
- Lateral - Hunger centers. Inhibited by leptin and destruction leads to anorexia and depression
- Ventromedial - Satiety center. Damage leads to hyperphagia and aggressive behavior. (craniopharyngoma)
- Suprachiasmatic - Circadian rythms, ADH production. OVLT zone that senses osmolality (Weak BBB)
- Suproptic - Sexually dimorphinc nucleus GnRH
- Paraventricular - Oxytocin
- Dorsomedial - Connections with orbitofrontal, smell and emotions, regultes BP, HR and GI (like VM with smell)
- Aruate: Dopamine (PRL) and GHRH
Posterior Pituitary
- ADH released, created in superchiasmatic hypothalamus
- Oxytocin released, made in paraventricular
Craniopharyngoma
- Tumor of surface ectoderm (epithelium) that was rathkes pouch (made anterior pituitary)
- Commonly presents in children as bitemporal hemianopia. May cause damage to hypothalmic structures and produce with their specific signs.
- Usually appears calcified on imaging.
Pituitary Adenoma
- Tumor of a specific type of cell in the AP.
- Most commonly secretes nothing, but does commonly secrete PRL.
- Most common in adults, presents as bitemporal hemianopia or ammenorrhea in women.
Wernicke Encephalopathy
- thiamine deficency in alcoholics
- Lesions of mamillary bodies of diencephalon
- Occular palsies, ataxic gate, and confabulations
Thalamic Sensory Nuclei
- Recieve information and send to brain
- VPL: Recieves all Sensory from body (P/T and Fine) DCML and ST
- VPM: Sensory from face (CN 5) and taste (CN 7,9,10)
- MG: Hearing, recieves input from superior olive and inferior colliculus (gaze reflexes). Outputs to temporal Lobe
- LG: Vision from optic nerve, projects to calcarine sulcus in occipital lobe.
Thalamic Motor Nuclei
VA/VL: VL is main output to cortex, VA is reciprocal with BG and Cerebellum
Thalamic Lesions
-Most commonly due to infarction from lenticulostriate (perforating branches of MCA) Lacunar HTN, and will result in contralateral loss of the given function.
Limbic Constiutuents
- Generates emotions, long term memory, smell, autonomics,
- Mamillary Bodies, Hippocampus, Amygdala, Cingulate Gyrus,
Papez circuit
-Hippocampus to mamillary bodies via Fornix. Then to anterior hypothalamus, to cingulate gyrus, to entorhinal cortex to hypothalamus
Wernicke Encephalopathy
-Hemorrhagic destruction to mamillary bodies due to severe thiamine deficency.
Most commonly seen in alcoholics
-Occular dysfunction, ataxia, confabulations
Kluver-Bucy
- Damage to the anterior temporal lobe (amygdala) results in hyperphagia, hypersexuality, docility.
- Most commonly caused by HSV (Likes to cause temporal lobe encephalopathy) in AIDS pts.
- Can also be caused by trauma and tumor
Foster Kennedy
- Increased ICP leads to damage of the optic nerve and the olfactory tracts
- Presents with anosmia and visual disturbances
- Caused by increased ICP (Tumor, etc)
Hippocampal Pathology
- Common site of siezure initiation
- Earliest site of damage in alzheimers
- Very sensitive to hypotension and hypoxia
Cerebellar Function and anatomy
- All function is ipsilateral.
- Inferior peduncle is sensory from ipsilateral cord
- Middle is from contralateral cortex input
- Superior is output to contralateral cortex
- Perkinje cells are only cells with output and it is inhibitory on VA/VL thalamus
Cerbellar parts
- Vermis functions for trunkal balance and outputs to the fastigal nucleus
- Paravermal is for trunkal and limb balance and outputs to eboliform and globos
- Lateral hemisphere is for coordination of movements of the limbs, outputs to dentate. Largest and most extensive connections
- Anterior is descending postural information, Posterior is information to cerebral cortex for motor planning and higher order functions
- Folculonodular is for balance and vestibular system
Cerebellar Injury
- Alcohol is most common and damages anterior vermis. Damages leg balance. Trunkal ataxia.
- Cerebellum is common site of tumor in kids
- Posterior cerebellar syndrome - upper trunkal ataxia
- Lateral Syndrome ataxia of ipsilateral side. Seen falling to ipsilateral side.
Basal Ganglia Structures
- Input from cortex to Caudate and Putamen.
- Caudate and putamen also recieve input from SNc
- Output is inhibitory only and via gpi/snr
Excitatory Pathway
-D1 receptors on striatum recieve input from snc. Leads to inhibition of Gpi/Snc. Which removes inhibiton of thalamus
Inhibitory BG
- D2 receptors inhibit the inhibitory pathway in striatum.
- Normally pathway has positive influence on STN which leads to increased stimulation of gpi/snr which leads increased inhibition of thalamus.
Parkinsons
- Depletion of dopaminergic neurons in snr.
- Can’t initiate movement. Leads to bradykinesia, resting tremor, gait instablity.
- Pathology shows lewy bodies with alpha synuclein inclusions.
- Late in the disease dementia will develop
Supranuclear Palsy
-Tau body formation with parkinson symtpoms and occular impairment. Tau will be present in BG and Brain stem
Tardive Dyskinesia
- Often permanent effect of antipsychotics that occurs because of increased sensitivity of dopamine in nigrostriatal pathway.
- Usually begins with mouth smacking and results in complete atheosis. Less common with atypical antipsychotics
Huntingtons Disease
- AD CAG repeat leads to death of cells in the caudate and caudate atrophy. Mediated by glutamate toxicity and NMDA-R.
- Shows anticipation with increasing CAG repeats occuring during spermatogenesis.
- Presents with athetosis that wil progress to aggression, depression, often commit suicide.
- Loss of GABA and Ach
Hemibalism
- HTN induced lacunar infarct of STN. Loss of STN is a loss of inhibitory pathway.
- Flinging athetotic movements.
- Lesion is in contralateral STN
Myoclonus
- Unsustained spasm of muscle
- Common and seen in siezures
- Rapid slow wave depolarization on EEG
- Seen in Critzfeld Jacob and other prion diseases
Dystonia
- Sustained spastic contraction of muscle
- Can treat with antiepileptic drugs and muscle relaxants.
Essential Tremor
- Tremor that is present at rest minimally and gets worse if try to hold in same position.
- Ethanol, beta blockers, and barbituates decrease.
MTPT
Street drug with metabolites that destroy neurons in snc. Parkinsons
Wilsons Disease
- Hepatolenticular degeneration.
- Copper deposits in basal ganglia and other structures
- Normally seen in 20’s with dementia, psychosis, and athetosis.
- Tx Peniclamine
Brocas Aphasia
Damage to the speech area on the dominant hemisphere in the frontal cortex. Motor aphasia.
- Can still comprehend but can’t speak
- MCA stroke
Wernickes aphasia
- Damage to speech area in temporal lobe.
- Receptive or sensory aphasia
- Occlusion of MCA
Conduction Apashia
-Damage to arcuate fassiculus which connects wernicke’s and brocas area.
-Can’t repeat, but can recieve and speak
MCA
Gerstmanns syndrome
- Damage to inferior parietal lobule on domninat side.
- Agraphia and acalcula
- MCA
Spacial Neglect Syndrome
- Damage to nondominant side inferior parietal lobule results in hemineglect
- MCA
Frontal Lobe Function and Damage
- Higher order processing and motor functioning
- Personality changes and cognitive changes
- Disihibition and return of primative relexes
- MCA or ACA
- Also motor
Reticular Activating System
- Located in midbrain, contains extensive cholinergic and adrenergic synapses.
- Damage leads to coma
Hippocampal Damage
- Anterograde amnesia is first sign
- Trauma, alzheimers
PPRF
- Lesion will cause nystagmus and occular gaze problems.
- Eyes will deviate away from lesion
Frontal Eye Field Damage
- Saccade damage and occular impairment
- Eyes will deviate towards lesion
Central Pontine Myelinolysis
- Extensive demylination of the pons, will appear as hyperintense on T2 weighted image
- Due to too rapid of correction in Na concentrations. Alcoholics or severely malnourishe
- Causes locked in syndrome.
Overview of ACA
- Arises from anterior circle of willis and supplies the inferior and medical aspects of the frontal and some parietal lobe.
- Occlusion will lead to loss of motor and sensory in the feet and legs (Homunclulus)
Overview of MCA
- Supplies the lateral frontal lobe, parietal, and some temporal
- Most commonly infarcts in smaller feeder arteries.
- Comes off internal carotid quickly so is common source of embolism and thrombus
- Will cause loss of motor and sensory to upper body and face (homunculus)
Overview of PCA
- Branch off vertebral artery, does communicate via circle of willis
- Supplies midbrain, temporal lobe, occipital lobe
Watershed areas
- Upper leg and arm weakness (ACA/MCA)
- Higher order processing (MCA/PCA)
Regulation of Cerebral Blood Flow
- Mainly autoregulation
- pCO2 greatly controls flow
- Dilates with increased pCO2
- Hyperventilation will lead to dilation of vessels by decreasing pCO2.
- At extremely low O2 saturation there will be dilation of cerebral vessels.
Lateral Striate Artery obstrucion
- Most commonly caused by HTN and hyaline arteriolosclerosis
- Generates lacunar infarcts
- BG, Internal Capsule
- Effects will be contralateral
- Anterior internal capsule is relay between BG, Cortex, Cerebellum.
- Genu- corticobulbar fibers (face paralysis)
- Posterior Limb - Corticospinal fibers leads to focal paralysis. (posterior also contains some optic and acoustic fibers.) Also contains blood supply from the internal carotid directly (anterior choroidal)
Anterior Spinal Artery Infarction
- Caudal Medial Medulla
- Loss of Motor from contralateral body, DCML
- Loss of hypoglossal nerve 12
- No motor or fine sensation, tongue deviates to the ipsilateral side
PICA infarction
- Lateral Medullary Syndrome
- Loss of: Vestibular, 9,10, (Nucleus Ambiguus), ST, SANS, Inferior cerebellar peduncle, Spinal 5.
- Loss balance, vertigo, nasuea (8), Fine touch contralateral body, Ataxia, dysmetria, P/T to face. Horners.
- Gag reflex, P/T contralateral body distinguish from AICA.
AICA
- Lateral inferior pons:
- Loss of 7,8. Middle/inferior cerebellar peduncles, SANS, Spinal 5
- Loss P/T to face, vertigo (8), ataxia/dysmetira, horners
- Loss hearing (cochlear), Facial motion (reflexes, tearing) ditinguish from PICA
PCA
- Occipital cortex
- Hemianopia with macular sparing
PCA paramedian
- Damage to midbrain
- CN 3, 4, UMN of 7
- Loss of motor to contralateral lower face.
Medial branches of basilar caudal pons
-DCML, Corticospinal, Abducens
Prinauds
- Tumor of pineal gland (pinealoma or dysgerminoma) often calcified on imaging
- Hydrocephalus
- Superior Colliculus : Upward and downward gaze palsy
Schwannoma
- Occurs at cerebellopontine angle. Involves CN 8. May not damage 7.
- Occurs bilaterally in NF2
- Classically: hearing loss and balance 8, spinal 5