Transtentorial herniation.
Can lead to duret haemorrhages due to stretching if arteries
Brain stem is pushed down by herniation causing shearing/ tearing of arteries
Frontal eye field.
Brodmann’s area 8
Control of horizontal conjugate gaze
Located in middle frontal gyrus
Halo sign.
Used to determine if there is CSF in nose fluid (after trauma)
Cerebrospinal rhinorrhea
What neurons are made of pseudounipolar and bipolar types?
Pseudounipolar: all first order neurons of the spinal cord and most first order neurons from cranial nerves
Bipolar: cranial nerves I, II, and VIII
Chromatolysis.
PNS axon regeneration
Occurs in first 24-48 hours following injury
Nissl bodies move to periphery
Nucleus moves away from axon hillock
Axon repair.
24-36 hours - Wallerian degeneration (degeneration of distal portion of axon)
Chromatolysis
Slow axonal transport (1-5mm/day)
Neuronophagia occurs if axon does not recover
Neuron supportive tissue.
Two types: fibrous connective and glial
PNS only has fibrous connective (includes Schwann cells)
CNS has glial cells and meninges are fibrous connective
Lamina terminalis.
Forms from closure of anterior neuropores in 4th week
Forms front wall of thalamus
Chronology of development.
Week 3 - beginning of neural plate
Week 4 - completion of neural plate
Week 4/5 - development of primary vesicles
Week 6 - development of secondary vesicles
Weeks 12-22 - development of corpus callosum
4th month - myelination begins
4th-8th months - development of sulci and gyri
Periventricular leukomalacia.
White matter infarcts occurring during hypotensive episodes in premature infants
Can result in diplegia or quadriplegia
Potential cause of CP
Rachischisis.
Non-closure of posterior end of neural tube (opening down spine)
Holoprosencephaly.
One large ventricle and fusion of midline structures
Often associated with cyclopia
Porencephaly.
Cyst formation typically post-infarction
Large growth of cyst can compress ventricles
Lissencephaly.
Absence of gyri
Tuberous sclerosis.
Distinction in white and gray matter is lost leading to tubers (enlarged firm white gyri)
Seizures and retardation
Hydrancephaly.
Hemispheres are absent and replaced by two large CSF filled sacs.
Arnold-Chiari syndrome.
Herniation of cerebellar tonsils into foramen magnum
Type I: herniation <3mm
Type II: herniation includes vermis (symptomatic)
Type III: herniation if brain stem and cerebellum outside of skull
Type IV: type III plus lack of cerebellum
Dandy-Walker syndrome.
Very large dilation of 4th ventricle
Vermis is usually absent (sometimes no cerebellum)
Slow motor development and enlarged head
Treatment: positive pressure shunt
Coloboma.
Congenital defect resulting in a fissure of part of the eye
Usually iris (unlikely to impair vision)
If in retina, can impair vision
Heterochromia iridium.
Complete: one iris different from the other
Partial: part of one iris is a different colour
Affected iris lighter (hypopigmented): simple heterochroma
-Horner’s and Hirschsprung’s are often associated
Affected iris darker (hyperpigmented): Lisch nodules (NF1)
-commonly associated with Sturge-Weber syndrome
Nonencapsulated receptors.
1) Free/naked nerve endings: pain sensation
2) Merkel’s discs: slowly adapting for pressure in hairless skin
3) Hair follicle receptors: free nerve ending wrapped around a hair follicle
Encapsulated receptors.
1) Meissner’s corpuscles: rapidly adapting fine touch (two point discrimination, not homogenous distribution)
2) Pacinian corpuscles: rapidly adapting for vibration
3) Ruffini’s corpuscles: slow adapting stretch receptors in dermis of hairy skin
Neuromuscular spindle.
Detects length of extrafusal muscle
Two types of axons wrapped around intrafusal muscle: annulospiral and flower spray
Aloha and gamma motor neurons
Neurotendinous spindles/Golgi tendon organs.
A capsule of tendon fibres that are more loosely arranged and can be compressed - provides tension information
Provides and inhibitory effect - prevents too much tension on muscle
ALS.
Degeneration of UMN and LMNs
Loss of voluntary control of muscles and bowel/bladder control
Eye muscles usually spared
Cognition and ANS usually intact
Poliomyelitis.
Degeneration of LMNs resulting in flaccid paralysis and atrophy
Damage to anterior horns
Where do the dorsal column and spinothalamic tracts synapse in the thalamus?
Ventral posterolateral nucleus (VPL)
Location of nucleus gracilis and cuneatus.
2nd order neurons synapse at these nuclei in the caudal medulla
Axons then decussate and ascend as accurate fingers to the VPL of the thalamus
Transverse myelitis.
Inflammation of the spinal cord causes by infection
Symptoms similar to SC transaction and LMN damage (usually at one segment)
Inflammation results in demyelination
Can present rapidly
Tectospinal tract.
Reflex postural movements in response to visual stimuli
Receives input from optic tract in order to adjust body movement to eye movement
Rubrospinal tract.
Inhibits extensors and facilitates flexors
Synapses in red nucleus, decussates, and descends ipsilaterally
Vestibulospinal tract.
Facilitates extensors and inhibits flexors
Postural control and balance
Reticulospinal tract.
Medial (pontine) reticulospinal: ipsilateral extensors
Lateral (medullary) reticulospinal: mostly ipsilateral flexors
Damage results in reflex contraction to innocuous stimuli
Lower motor neuron symptoms.
Occur only at level of lesion:
Flaccid paralysis
Atrophy of muscles
Loss of reflexes
Muscular fasciculations
Muscular contracture (shortening of muscles)
Reactions of degeneration (decreased muscle response to electrical stimulation)
Anterior cord syndrome.
Bilateral LMN symptoms at lesion Bilateral UMN symptoms below lesion (not Babinski or loss of abdominal/cremasteric) Occlusion of anterior spinal artery CST and dorsal column spared Bilateral loss of spinothalamic
Central cord syndrome.
Bilateral LMN symptoms
Bilateral UMN paralysis with sacral sparing
Bilateral loss of pain, temperature, and light touch with sacral sparing
Occurs after hyper extension injury in an individual with long-standing cervical spondylosis
Brown-Sequard syndrome.
Ipsilateral LMN symptoms at level of lesion
Ipsilateral spastic paralysis, Babinski, and hyperreflexia below lesion
Ipsilateral loss of dorsal column
Contralateral loss of spinothalamic 1-2 segments below lesion
Complete sensory loss at ipsilateral level of lesion
Familial spastic paraparesis.
Loss of all corticospinal tracts
Extension of leg and flexion of arms
Subacute combined degeneration.
Caused by pernicious anemia
Degeneration of myelin
Paresthesias, leg stiffness, weakness, lethargy, fatigue, ataxia
Loss of dorsal columns and lateral corticospinal tracts
Friedreich’s ataxia.
5-15 years old Muscle weakness and ataxia Vision impairment, hearing loss, slurred speech Aggressive scoliosis Diabetes mellitus Enlarged heart
Machoda-Joseph disease.
Weakness in arms and legs Spasticity Staggering, lurching gait, often mistaken for drunkenness Nystagmus, diplopia, polyuria Difficulty with speech and swallowing
Spastic bladder.
Damage above T12
Urination is involuntary, frequent and caused by spasms in lower limbs
Lacking sensation of full bladder
Atonic (flaccid) bladder.
Direct injury to peripheral innervation of the bladder or lesion to cord around S2-S4
Retention with overflow incontinence
Horner’s syndrome.
Interruption of the oculosympsthetic pathway
Can result from hypothalamic lesion, brain stem, plexus, or spinal cord lesion or compression or superior cervical ganglion
Ptosis, miosis, anhydrosis, enophthalmos, loss of ciliospinal reflex
Damage to Edinger-Westphal nucleus.
Internal ophthalmoplegia (blown pupil)
Fixed and dilated pupil
Loss of accommodation reflex (cycloplegia)
Adie’s pupil/Adie’s syndrome.
Damage to ciliary muscles or ciliary ganglion
Fixed and dilated pupil
If affects dorsal root ganglion = Adie’s syndrome
Decreased deep tendon reflexes, anhydrosis, postural hypotension, and unsteady heart rhythms
Autonomic dysreflexia.
Spinal cord injury at or above T6 causing exaggerated sympathetic response from interruption of ANS control by higher centers
Severe headache, hypertension, tachycardia, fever, profuse sweating above injury level, and dry skin below
Familial dysautonomia (Riley-Day syndrome).
Ashkenazi Jewish descent
Loss of autonomic and sensory ganglia neurons
Abnormal sweating
Unstable BP
Difficulty feeding
Progressive sensory loss
Multiple system atrophy (Shy-Drager syndrome).
CNS degeneration
Orthostatic hypotension, anhydrosis, impotence and atonic bladder
Can show Parkinsonism symptoms
Lambert-Eaton myasthenic syndrome.
Presynaptic defect in Ach release
Weakness of limb muscles but not bulbar muscles
Muscle strength improves with use
Anaphylactic shock syndrome.
Severe allergic reaction: bronchoconstriction, system vasodilation, and severe hypotension
Epinephrine treatment:
Beta 1 - increases heard rate
Beta 2 - bronchiole dilation
Alpha 1 - peripheral vasoconstriction
Weber syndrome.
Medial midbrain syndrome or superior alternating syndrome
Paramedian branch of PCA
CN III axons: ipsilateral ptosis, mydriasis and down and out eye
Corticospinal and corticobulbar
Benedikt’s syndrome.
Short circumflex branch of PCA
Para median midbrain syndrome
Ocular deficits: CN III Cerebellar ataxia (red nucleus) Medial lemniscus (contralateral symptoms)
Parinaud’s syndrome.
Dorsal midbrain syndrome
Lesion to superior colliculi
Usually caused by pineal gland tumor
Paralysis of upward and downward gaze
Pupillary disturbances
Absence of convergence
Medial longitudinal fasciculus.
Extends throughout brain stem
Connects CN III, IV, VI, and VIII
Medial inferior pontine syndrome.
Foville’s syndrome
Occlusion of branches of basilar artery
CN VI damage: medial deviation Corticobulbar damage (contralateral) Corticospinal damage (contralateral) Damage to pontine nuclei on one side and pontine fibres on the other - bilateral limb and gait ataxia Medial lemniscus damage (contralateral)
Lateral inferior pontine syndrome.
Occlusion of AICA
CN VII: ipsilateral facial paralysis, loss of taste anterior 2/3, loss of corneal and stapedial reflexes
CN VIII: unilateral central nerve deafness, nystagmus, nausea, vomiting, and vertigo
Cerebellar peduncles: ipsilateral limb and gait ataxia
Spinothalamic: contralateral
Descending sympathetic tract: ipsilateral Horner’s syndrome
Lateral superior pontine syndrome.
Occlusion of superior cerebellar artery
Middle and inferior cerebellar peduncles: ipsilateral limb and trunk ataxia
Spinothalamic and spinotrigeminal: contralateral pain and temperature body, and ipsilateral for head
Descending sympathetic tract: ipsilateral Horner’s
Medial lemniscus: contralateral from lower limbs
Locked in syndrome.
Infarction at the base of the pons
Corticospinal and corticobulbar
Quadriplegia and paralysis of lower CNs
Can only blink or move eyes vertically
Central pontine myelinolysis.
Demyelination of central pons in patients being treated for hyponatremia or alcohol withdrawal
If treatment is too rapid - bilateral demyelination
Lateral medullary syndrome.
Inferior alternating syndrome or PICA syndrome
Occlusion of PICA or vertebral artery
Nucleus ambiguous: CN IX, X, and XI dysphagia and dysarthria
Trigeminal: ipsilateral loss of pain and temperature on face
Vestibular nuclei/inferior peduncle: vertigo, nausea, vomiting, nystagmus
-ataxia
Spinothalamic: contralateral pain and temperature
Horner’s syndrome (ipsilateral)
Medial medullary syndrome.
Inferior alternating syndrome or Dejerne syndrome
Occlusion of anterior spinal artery or vertebral artery
Contralateral hemiparesis (corticospinal) Loss of dorsal column Ipsilateral paralysis of tongue muscles (hypoglossal)
Anterior commissure.
Decussatimg axons from CN I
Connection between amygdalas
Conveys some acute neospinothalamic pain information
Uncus.
Part of temporal lobe
Primary olfactory area found here (area 34)
Portion that herniated in transtentorial herniation
Tensor tympani.
Innervated by CN V (SVE)
Attached to malleous of the inner ear and decreases noise from chewing by inhibiting movement of malleolus
Damage could result in hypoacusis to low frequency sounds
Bell’s palsy.
Swelling of CN VII in facial canal Ipsilateral Upper and lower facial paralysis Loss of lacrimal ion Decreased salivation Loss of taste anterior 2/3 of tongue Hyperacusis (stapedius muscle paralysis)
Foster Kennedy Syndrome.
Meningioma of the olfactory groove
Compresses olfactory tract and optic nerve
Ipsilateral anosmia and contralateral papilledema (damage to ipsilateral optic nerve)
Loss of vision bilaterally (damage to one optic nerve)
Gustatory ganglions and nerves.
Gustatory cells from taste bud synapse with first order neurons at these ganglia:
Nodose (CN X)
Petrosal (CN IX)
Geniculate (CN VII)
First order neuron goes to solitary nucleus in brain stem which projects to VPM, hypothalamus, amygdala, gustatory cortex, and hippocampus
Caloric test.
Tests for brain stem damage
Normal: cool water in ear canal results in nystagmus towards opposite side and warm water results in nystagmus toward the same side
COWS = cool opposite, warm same
Otosclerosis.
Fixation of the stapes
Age related
Ménière’s disease.
Increased endolymph pressure
Fluctuating hearing loss
Roaring tinnitus
Recurrent spinning vertigo
Acoustic neuroma.
Made of Schwann cells, benign, not age related
CN VIII is initially affected followed by CN V and CN VII
Hyperacusis.
Stapedius muscle is attached to the stapes. Loud noises result in contraction of the muscle, dampening sound transduction normally.
Paralysis of muscle or damage to CN VII results in hyperacusis wherein loud noises are not dampened
Ballismus.
Stroke induced
Involuntary flinging of contralateral limbs
Sub thalamus nucleus damage
Sinemet.
L-dopa/Carbidopa combination
Carbidopa decreases degradation of L-dopa in systemic circulation
Lower doses = less side effects
Most common movement disorders.
1) Essential tremor
2) Parkinson’s Disease
3) Dystonia (lentiform)
Internal capsule.
Corticostriate and corticopontine go through anterior limb
Corticobulbar, corticospinal, corticofugal for extra pyramidal tracts, and 3rd order neurons from VPL and VPM go through posterior limb
Anterior (genu) lesions.
Akinetic mutism (do not move or speak) Tactile agnosia
Posterior (splenium) lesions.
Alexia without agraphia
Conduction aphasia.
Lesion to the arcuate fasciculus
Difficulty with repeating words or automatic lists (ABCs)
Transcortical motor aphasia.
Area near Broca’s is damaged
Arcuate fasciculus is intact
Repetitive speech is intact
Like Broca’s
Transcortical Wernicke’s aphasia.
Damage near Wernicke’s area
Speech is fluent and grammatical and repetition is good
Tend to substitute similar words often
Balint’s syndrome.
Bilateral lesions to parietal and occipital lobes
Optic ataxia (inability to visually guide hands) Optic apraxia (inability to voluntarily control gaze) Simultagnosia
Gerstmann’s syndrome.
Damage to area 39 angular gyrus
Contralateral heme- or quadrantinopia Right-left confusion Finger agnosia Agraphia Dyscalculia