Chapter 12 - Neurology Flashcards
1
Q
What is the difference between hypotonia and weakness?
A
- hypotonia is decreased resistance to passive stretching
- weakness is decreased force generated by active muscle contraction
2
Q
What is the difference between central and peripheral hypotonia?
A
- central is dysfunction of upper motor neurons; it more often presents with altered level of consciousness and increased DTRs
- peripheral is dysfunction of lower motor neurons; typically presents with normal level of consciousness, diminished muscle bulk, and absent DTRs
- both typically present with weak cry, decreased spontaneous movement, a frog-leg posture, and muscle contractures
3
Q
What history and physical exam findings are consistent with central and peripheral hypotonia?
A
- in the history, central is often associated with neonatal seizures whereas peripheral is associated with decreased fetal movements and breech presentation
- both tend to present with weak cry, decreased spontaneous movement, a frog-leg posture, and muscle contractures
- central tends to present with altered level of consciousness and increased deep tendon reflexes
- whereas peripheral generally presents with a normal level of consciousness but decreased muscle bulk and absent deep tendon reflexes
4
Q
What is the differential for central hypotonia?
A
there are acquired causes - electrolyte abnormality - hypoxic-ischemic injury - sepsis or meningitis - intracranial hemorrhage - trauma and congenital causes - cerebral malformation - chromosomal disorder like Down's or Prader-Willi - metabolic disorders
5
Q
What is the differential diagnosis for peripheral hypotonia?
A
- spinal muscular atrophy
- familial dysautonomia affecting peripheral nerves
- botulism, neonatal myasthenia, and magnesium toxicity which all impact the neuromuscular junction
- congenital muscular dystrophy or myotonic dystrophy, metabolic myopathies like Pompe’s disease, or structural myopathies
6
Q
What does the work up for central hypotonia involve?
A
- head CT to look for CNS injury or congenital malformation
- serum electrolytes to rule out metabolic disorders
- chromosomal studies
7
Q
What does the work up for peripheral hypotonia involve?
A
- serum creatine kinase levels
- DNA tests for spinal muscular atrophy
- nerve conduction studies to identify myasthenic disorders
- muscle biopsy
8
Q
Spinal Muscular Atrophy
A
- an autosomal recessive disease leading to anterior horn cell degeneration and infiltration of microglia and astrocytes
- caused by a mutation in the survival motor neuron gene on chromosome 5
- the major features are peripheral hypotonia, weakness, and tongue fasciculations; patients often have a bell-shaped chest and frog-leg posture; extra ocular movements and sensory examination are normal
- classified as type I (aka Werdnig-Hoffman disease) with an onset before 6 mo, type II with onset between 6-12mo, and type III with onset after 3 yo
- diagnosed based on DNA testing
- treatment is supportive
- death is within the first year, during adolescence, or in adulthood based on the type, and death is typically due to respiratory failure
9
Q
What is the most common hereditary neuromuscular disorder?
A
Duchenne muscular dystrophy
10
Q
Infantile Botulism
A
- a peripheral hypotonic disorder characterized by bulbar weakness and paralysis during the first year of life, secondary to ingestion of C. botulinum spores
- spores classically contaminate honey and go on to produce a toxin which prevents presynaptic release of acetylcholine
- constipation is classically the first symptom; neurologic symptoms typically follow and include weak cry and suck, loss of previously obtained motor milestones, ophthalmoplegia, and hyporeflexia; the paralysis is symmetric and descending
- diagnosed based on identification of the toxin o bacteria in the stool and an incremental response during high-frequency EMG stimulation
- treatment is mostly supportive but botulism immune globulin is available; antibiotics are contraindicated and may worsen the clinical course
- recovery is expected by may take weeks or months
11
Q
Congenital Myotonic Dystrophy
A
- a disorder that presents in the newborn period with weakness and peripheral hypotonia before progressing to myotonia
- it is an autosomal dominant trinucleotide repeat disorder affecting a gene on chromosome 19, which is transmitted primarily by an affected mother
- patients often have a history of polyhydramnios secondary to a poor swallow as well as decreased fetal movements
- at birth patients have feeding and respiratory problems as well as facial diplegia, peripheral hypotonia, and arthrogryposis
- myotonic facies, ptosis, a stiff straight smile, and an inability to release the grip after hand-shaking present in adulthood
- course may be complicated by mental retardation, cataracts, cardiac arrhythmias, and infertility
- diagnosed according to DNA testing
- treatment is supportive and the prognosis is poor as many die from respiratory failure or all survivors have mental retardation with an IQ between 50-65
12
Q
Hydrocephalus
A
- increased CSF under pressure
- classified as non-communicating due to obstruction or communicating due to increased production or reduced absorption
- can be congenital, likely due to chiari type II, Dandy-Walker malformation, or congenital aqueductal stenosis, which are all obstructive
- or it can be acquired via intraventricular hemorrhage, bacterial meningitis (reduces absorption), or brain tumors (increases production)
- presents with increasing head circumference, large fontanelles, prominent scalp veins, and “sunset sign” (downward deviation of eyes caused by an enlarged third ventricle pressing on the upward gaze center in the midbrain) in those with open cranial sutures
- presents with headache, n/v, unilateral sixth nerve palsy, papilledema, and brisk DTRs in older children with closed sutures
- requires urgent head CT and placement of a ventriculoperitoneal shunt
13
Q
Define “spina bifida” and “neural tube defect”.
A
- spina bifida is any failure of bone fusion in the posterior midline of the vertebral column
- neural tube defect is a term that includes all forms of failure of neural tube closure from anencephaly to sacral meningocele
14
Q
What are spina bifida occult, meningocele, and myelomeningocele?
A
- spina bifida occult is a vertebral cleft without herniation of any neural or meningeal tissue
- meningocele is a herniation of the meninges only, usually without any associated neural deficits
- meningomyelocele is a herniation of the meninges and spinal cord tissue, resulting in neural deficits
15
Q
Neural tube defects have the highest and lowest incidence in which countries?
A
- highest in Ireland
- lowest in Japan
16
Q
What is used to prevent neural tube defects?
A
prenatal folic acid supplementation
17
Q
What teratogens are known to cause spina bifida?
A
- valproate is the leading example
- others include phenytoin, colchicine, vincristine, azathioprine, and methotrexate (which affect folic acid metabolism)
18
Q
Describe the presentation of meningocele and meningomyelocele.
A
- bother present with a fluctuant midline mass filled with CSF and/or spinal cord tissue
- since meningoceles are filled only with CSF, they can be transilluminated
- unlike meningoceles, meningomyeloceles often have associated neurologic deficits which depend on the levell of the lesion but range from paraplegia to bladder and bowel incontinence
19
Q
Meningomyelocele
A
- a form of spina bifida and neural tube deficit in which there is herniation meningeal and neural tissue
- teratogens which may lead to this defect include valproate, phenytoin, colchicine, vincristine, azathioprine, and methotrexate while prevention relies on folic acid supplementation
- presents as a midline, fluctuant mass with neurologic deficits depending on the level of the lesion
- most are associated with a chair type II malformation and hydrocephalus; some are associated with cervical hydrosyringomyelia, defects in neuronal migration and genesis of the corpus callosum, orthopedic problems, or GU defects
- diagnosed based on elevated AFP in the amniotic fluid and maternal serum; fetal sonography is also highly sensitive
- requires urgent surgical repair within 24 hours to reduce the risk of infection or trauma to the exposed tissue
20
Q
What is cervical hydrosyringomyelia?
A
an accumulation of fluid within the central spinal cord canal and within the cord itself
21
Q
What are the most common causes of coma in pediatrics?
A
- in children younger than 5yo, non accidental trauma and near-drowning are the most common causes
- in older children drug overdose and accidental head injury are most common
22
Q
When assessing an individual in a coma, what are the most important goals?
A
- determine the depth of coma
- identify neurologic signs that may indicate the site or cause of the coma
- monitor the patients recovery and ensure stability
23
Q
CSF or blood draining from the nose or auditory canal is indicative of what?
A
a basilar skull fracture
24
Q
What do the following motor responses indicate about a comatose patient:
- flaccidity or no movement
- decerebrate posturing
- decorticate posturing
- asymmetric responses
A
- flaccidity or no movement: severe spinal or brainstem injury
- decerebrate posturing: indicates subcortical injury
- decorticate posturing: indicates bilateral cortical injury
- asymmetric responses: suggests hemispheric injury
