Central Nervous System Flashcards
Neural Tube Defects
Incomplete closure of the neural tube.
Associated with low folate levels PRIOR to conception
Detected by elevated alpha-fetoprotein (AFP) levels in the amniotic fluid and maternal blood
Ancephaly
Absence of skull and brain resulting in “frog like appearance”
Results in maternal polyhydraminos since the swallowing of amniotic fluid by the fetus is impaired
Spina Bifida
Failure of the posterior vertebral arch to close resulting in a vertebral defect.
Spina Bifida occulta = dimple or patch of hair overlying the vertebral defect
Typically presents with cystic protrusion of the udnerlying tissue through the vertebral defect
Meningocele = protrusion of meninges into cyst
Meningomyelocele = protrusion of meninges and spinal cord
Meningocele
NTD with protrusion of meninges into cyst
Meningomyelocele
NTD with protrusion of meninges and spinal cord
Pathway of CSF
CSF produced by choriod plexus lining the ventricles
Moves into 3rd ventricle via interventricular foramen of Monro
Flows from 3rd to 4th via cerebral aqueduct
flows from 4th ventricle into subarachnoid space via foramina of magendie and Luschka
Cerebral Aqueduct Stenosis
Presents with enlarging head circumference due to dilation of the ventricles (remember the cranial sutures have not yet fused)
Dandy Walker Malformation
Congenital failure of the cerebral vermis to develop
Presents as massively dilated 4th ventricle (posterior fossa) with an ABSENT cerebellum
Usually accompanied by hydrocephalus
Arnold Chiari Malformation (Type II)
Congenital downward dispalcement of the cerebellar vermis and tonsils through the foramen magnum
Obstruction of CSF flow commonly results in hydrocephalus
Can occur in association with meningomyelocele (most cases) and syringomyelia
Syringomyelia
Cystic degeneration of the spinal cord usually at C8-T1
Arises with trauma or in association with and Arnold Chiari Malformation
Presents as sensory loss of pain and temperature with sparing of fine touch and position sense in the upper extremities (“cape like” distribution) - due to involvement of the anterior white commisure of the spinothalamic tract with sparing of the dorsal column
Can expand to involve other tracts
1) Lower motor neurons of Anterior Horn = muscle atrophy and weakness with decreased muscle tone and impaired refelces
2) Lateral horn of Hypothalamic Tract - Horner’s Syndrome,
ptosis (droopy eyelid), miosis (constricted pupil), anhidrosis (decreased sweating)
Horner’s Syndrome
ptosis (droopy eyelid), miosis (constricted pupil), anhidrosis (decreased sweating)
Can be caused when get lesion of the hypothalamic tract
Poliomyelitis
Poliovirus infects the anterior motor horn
Get lower motor neuron signs = flaccid paralysis with muscular atrophy, fasiculations, weakness with decreased muscle tone, impaired reflexes, and negative babinski sign
Lower Motor Signs
Seen with lesions of Anterior motor horn flaccid paralysis with muscular atrophy, fasiculations, weakness with decreased muscle tone, impaired reflexes negative babinski sign
Upper Motor Signs
Seen with lesions of Lateral Corticospinal tract
spastic paralysis with hyperreflexia,
increased muscle tone,
positive Babinski sign
Werdnig Hoffman Disease
Inherited degeneration of anterior motor horn, autosomal recessive
“floppy baby” and death occurs a few years after birth
Amyotrophic Lateral Sclerosis (ALS)
Degenerative disorder of upper and lower motor neuron signs
Earliest sign is usually atrophy and weakness of hands
LACK of sensory impairment distnguishes it from syringomyelia
Normally sporadic and occurs in middle aged but also see in inherited mutation in Zinc-copper superoxide dismutase mutation (SOD1)
Anterior horn = lower motor signs = flaccid paralysis with muscular atrophy, fasiculations, weakness with decreased muscle tone, impaired reflexes, and negative babinski sign
Lateral Corticospinal tract = upper motor neuron signs = spastic paralysis with hyperreflexia, increased muscle tone, and positive Babinski sign
Zinc-copper superoxide dismutase mutation (SOD1)
Mutation can be inherited and lead to ALS
Get free radical injury in neurons
Friedrich Ataxia
Degenerative disorder of the cerebellum and spinal cord
Autosomal recessive, expansion of unstable trinucleotide repeat (GAA) in the frataxin gene = loss of mitochondrial iron regulation, buildup of Fe and get free radical damage
Get ataxia and then loss of different tracks can result in loss of vibratory sense and proprioception, muscle weakness in lower extremities, and loss of deep tendon reflexes
Often associate with hypertrophic cardiomyopathy
Presents in early childhood and patients are soon wheelchair bound
Frataxin Gene
Autosomal recessive loss = Friedrich Ataxia
Gene involved in mitochondrial Iron regulation.
Expansion of unstable trinucleotide repeat (GAA) leads to defective gene and get iron buildup and free radical damage that leads to the symptoms of Friedrich Ataxia
Layers of the meninges
Brain –> Pia –> Arachnoid–>Dura–>Skull
Leptomeninges
The pia and arachnoid together are termed the leptomeninges
Meningitis
Inflammation of the leptomeninges. Can be caused by bacteria, viral, or fungal.
Presents with triad of (1) headache (2) nuchal rigidity (3)fever but can also see photophobia (especially in viral), vomiting and altered mental status
Complications include death due to herniation secondary to cerebral edema, hydrocephalus/hearing loss/seizures due to fibrosis.
Bacterial meningitis is much more serious
Cause of Meningitis in neonates
Group B Strep (from vagina in the birthing canal)
E coli
Listeria Monocytogenes
Cause of meningitis in children and teenagers
N Meningitidis (enters through the nasopharynx then to blood and then to meninges) Coxsackie virus (fecal-oral) can also cause meningitis in children
Cause of meningitis in Adults and elderly
Streptococcus pneumoniae
Cause of meningitis in non-vaccinated infants
H Influenza
CSF findings in bacterial meningitis
Neutrophils with decreased CSF glucose
CSF findings in Viral meningitis
Lymphocytes with normal CSF glucose
CSF Findings in Fungal Meningitis
Lymphocytes with decreased CSF glucose
Neutrophils with decreased CSF glucose
CSF findings in bacterial meningitis
Lymphocytes with normal CSF glucose
CSF findings in Viral meningitis
Lymphocytes with decreased CSF glucose
CSF Findings in Fungal Meningitis
Lumbar puncture and layers crossed
Sample CSF. Perform between L4 and L5 =illiac crest (since spinal cord ends at L2 but cauda equina continues to S2)
Cross skin, ligaments, epidural space, dura, and arachnoids
Etiologies of Global Cerebral Ischemia
Low perfusion (ex atherosclerosis)
Acute decrease in blood flow (cardiogenic shock)
Chronic hypoxia (anemia)
Repeated episodes of hypoglycemia (insulinoma)