31: Atypical and Inherited Motor Neuron Disorders Flashcards
When worried about atypical motor neuron disorder, what are you thinking with acute onset of symptoms?
Paralytic polio, West Nile encephalitis, acute flaccid myelitis
When worried about atypical motor neuron disorder, what are you thinking with predominantly lower motor neuron signs?
MMNCB, Kennedy, SMA;
radiation injury, paralytic polio, West Nile, acute flaccid myelitis;
Monomelic amyotrophy (Mirayama)
When worried about atypical motor neuron disorder, what are you thinking with sensory symps and/or signs?
HTLV-1 and -2 associated myelopathy;
Adult polyglucosan body disease;
Late-onset Tay-Sachs disease;
Kennedy
When worried about atypical motor neuron disorder, what are you thinking with B/B dysfxn?
HTLV-1 and -2 associated myelopathy;
adult polyglucosan body disease
When worried about atypical motor neuron disorder, what are you thinking with cerebellar, extrapyramidal, cognitive, and/or psych dysfxn?
Late-onset Tay-Sachs;
hereditary spastic paraplegia;
adult polyglucosan body disease
When worried about atypical motor neuron disorder, what are you thinking with duration longer than 5 yrs?
Kennedy disease; radiation injury; late-onset Tay-Sachs;
SMA, hereditary spastic paraplegia, adult polyglucosan body disease
When worried about atypical motor neuron disorder, what are you thinking with onset before age 40?
Late-onset Tay-Sachs disease;
familial ALS;
SMA, hereditary spastic paraplegia, monomelic amyotrophy
When worried about atypical motor neuron disorder, what are you thinking with positive family history?
Kennedy disease; familial ALS; late-onset Tay-Sachs;
SMA, hereditary spastic paraplegia, adult polyglucosan body disease
Likely causes nowadays for paralytic poliomyelitis? Key presentation?
Coxsackievirus, echovirus, enterovirus (EV-D68);
fever, headache, myalgias, GI disturbance;
weak, wasting, depressed reflexes, weakness typically in LE and asymmetric
For polio, what do you look for in pre-paralytic phase of illness?
Lymphocytic pleocytosis (100-200 cells per cubic mm)
West Nile Encephalitis is caused by what virus? How can diagnosis be made?
Member of flavivirus family;
IgM Ab’s to West Nile virus in CSF or serum
With West Nile Encephalitis, what can be seen on Edx studies?
Typically reduced CMAP amplitudes, and needle EMG with evidence of axonal loss
Where is HTLV-1 endemic? What is seen there as opposed to ALS?
Caribbean, Japan, southeast US, Italy, sub-Saharan Africa;
can see spastic paraparesis and HTLV-1 associated myelopathy, with minor sensory findings or bladder dysfxn
With familial ALS, what are the typical mutations? Typical inheritance pattern?
C9orf72 (open reading frame); then SOD-1, then TDP-43 (transactive response DNA-binding protein), and then FUS (fused-in-sarcoma);
AD
What is most likely inheritance pattern gene-wise of SMA?
SMN1 gene mutation on chromosome 5q
What is prominent with X-linked bulbospinal muscular atrophy (Kennedy Disease)?
Look for proximal muscle and later bulbar involvement;
see facial fasciculations that worsen with contraction like whistling or blowing out cheeks;
also can see gynecomastia with other endocrine abnormalities like DM
With X-linked bulbospinal muscular atrophy (Kennedy Disease), what is seen on Edx studies? What lab could be affected?
Can see low CMAP amplitudes;
low-amplitude or absent SNAP’s are key as there is degen of the DRG;
needle EMG shows grouped repetitive motor unit discharges with activation of the facial muscles;
slightly elevated CK
What are a few manifestations associated with hereditary spastic paraplegia?
Ataxia, seizures, dementia, intellectual disability;
optic neuropathy, retinopathy, peripheral neuropathy, amyotrophy, deafness
(SAID go on the PERIPHERAL ROAD)
What accumulates in late-onset Tay-Sachs disease?
GM2 ganglioside due to deficiency of Hexosaminidase A
What muscles tend to get involved with adult-onset hexosaminidase A (Tay-Sachs) deficiency? What can be seen on Edx studies?
Lower extremities first, more so the proximal muscles (quad);
in UE, usually the triceps;
maybe low CMAP amplitudes, possible abnormal SNAP’s, look for CRD’s
What concurrent signs to look for with adult-onset Hexosaminidase A (Tay-Sachs) deficiency? How to make definitive diagnosis?
Cerebellar and/or psych signs, or FH;
measure Hexosaminidase A activity in serum, leukocytes, or fibroblasts
Hallmark of adult polyglucosan body disease? What is the mutation and inheritance pattern?
Large number of polyglucosan bodies (resemble Lafora bodies or corpora amylacea) in central and peripheral neuronal processes and astrocytes;
Glycogen branching enzyme gene (GBE1) and AR
What can be seen with diagnostic studies for adult polyglucosan body disease (APGBD)?
Can see mild-to-moderate slowing of motor nerve CV and low-amplitude or absent SNAPs;
Can see periventricular and subcortical white matter abnormalities on MRI;
pathology is definitive (intra-axonal polyglucosan bodies)
With monomelic amyotrophy, what muscles are usually affected? What can aggravate weakness?
C7-T1 muscles;
cold (cold paresis)
What is notable on Edx studies with monomelic amyotrophy? What other study to order?
Can see potentially low median or ulnar CMAP amplitudes; SNAPs preserved; MRI with contrast of C-spine in FLEXION
What ratio to look for with monomelic amyotrophy?
ADM/APB CMAP amplitude ratio of < .6 (opposite of ALS)
What is seen with delayed radiation-induced motor neuron syndrome?
Usually lower motor neuron weakness in LE after radiation exposure;
look for low CMAPs with intact SNAPs, and fib potentials on EMG;
look for myokymic discharges
