mnd - other than als
TRANSCRIPT
8/6/2019 MND - other than ALS
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OTHER MOTOR NEURONOTHER MOTOR NEURON
DISEASESDISEASES
LOWER MOTOR NEURON DISORDERS
The peripheral motor neurons are affectedwithout evidence of involvement of the corticospinal
motor system
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XX--LinkedLinked SpinobulbarSpinobulbar MuscularMuscular
Atrophy (Kennedy's Disease)Atrophy (Kennedy's Disease)
y Progressive weakness and wasting of
limb and bulbar muscles begins in males inmid-adult life and is conjoined with
androgen insensitivity manifested by
gynecomastia and reduced fertility
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y Distinguishing features from ALS-absence
of spasticity and presence of subtle
sensory neuropathy.
y The underlying molecular defect is an
expanded trinucleotide repeat (-CAG-) in
the first exon of the androgen receptorgene on the X chromosome.
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AdultAdult TayTay--Sach'sSach's DiseaseDisease
y Arising from deficiency of the enzyme B-
hexosaminidase (hex A).
y They are very slowly progressive .
y Dysarthria and radiographically evident
cerebellar atrophy may be prominent.
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Spinal Muscular AtrophySpinal Muscular Atrophy
y Early onset
y Defect in the majority of families with
SMA maps to a locus on chromosome 5
encoding a putative motor neuron
survival protein (SMN, for survival motor
neuron)
y Characterized by extensive loss of largemotor neurons; muscle biopsy reveals
evidence of denervation atrophy.
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Multifocal Motor Neuropathy withMultifocal Motor Neuropathy with
Conduction Block Conduction Block
y Lower motor neuron function isregionally and chronically disrupted byremarkably focal blocks in conduction.
y Elevated serum titers of mono- andpolyclonal antibodies to ganglioside GM1;which produce selective, focal, paranodal
demyelination of motor neurons.y Respond dramatically IV immunoglobulin
or chemotherapy
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SELECTED DISORDERS OF THESELECTED DISORDERS OF THE
UPPER MOTOR NEURONUPPER MOTOR NEURON
y Primary Lateral Sclerosis
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y Rare disorder arising sporadically in adults
in mid- to late life.
y Characterized by progressive spastic
weakness of the limbs, preceded or
followed by spastic dysarthria and
dysphagia, indicating combined
involvement of the corticospinal andcorticobulbar tracts.
Primary Lateral SclerosisPrimary Lateral Sclerosis
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y Neuropathologic examination reveals loss
of the large pyramidal cells in the
precentral gyrus and degeneration of the
corticospinal and corticobulbarprojections.
y Variable course.
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FAMILIAL SPASTIC PARAPLEGIAFAMILIAL SPASTIC PARAPLEGIA
y Autosomal trait usually.
ySymptoms -progressive spastic
weakness beginning in the distal lowerextremities.
y Respiratory function is spared-Has a long
survival.
y Late in the illness there may be urinary
urgency and incontinence and sometimes
fecal incontinence
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yWhen recessively inherited- altered
corticospinal and dorsal column function
accompanied by amyotrophy, mental
retardation, optic atrophy, and sensoryneuropathy.
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NEUROPATHOLOGYNEUROPATHOLOGY
y Degeneration of the corticospinal tracts,
which appear nearly normal in the
brainstem but show increasing atrophy at
more caudal levels in the spinal cord-distal axonopathy of long neuronal
f ibers within the CNS.
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y Eleven FSP genes have been identified.
y Spastin-The gene most commonlyimplicated in dominantly inherited FSP,
encodes a microtubule interacting protein.
y
Atlastin-The most common childhood-onset dominant form arises from mutations
in this gene.
y Gene for myelin proteolipid protein-
mutation causes X-linked recessive FSP.
y par apleg in gene- recessive variant.
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