Download Anterior horn cell disorders Lower motor neurons The LMNs are

Anterior horn cell disorders
Lower motor neurons
The LMNs are located in the brainstem and spinal cord
The spinal LMNs are also known as anterior horn cell. Dorsal anterior horn cells innervate distal
muscles, ventral located cells- proximal muscles, medially located neurons- truncal and axial
muscles.
Large spinal cord LMNs are called alpha neurons.
Signs and Symptoms of Lower Motor Neuron Dysfunction
Weakness: denervation as well as decreased number of functional LMN units reduces
overall muscles strength.
Muscle atrophy and Hyporeflexia
Muscle hypotonicity and flaccidity
Fasciculations
Muscle cramps
Motor Neuron Disease
Incidence/100,000/year : Overall: 1.5 to 2
Age : 65 to 74 years
Prevalence: 3 to 8 per 100,000
Risk increases with age up to 74 years
Mortality
Causes 1 in 700 deaths
Rate: 1.9/100,000/year
Male:Female 1.5:1
More male predominance in younger onset cases
Clinical features
Typical pattern: Upper + Lower motor neuron signs with normal sensation
Onset & Patterns of weakness: Common features
Asymmetric limb weakness :
Upper > Lower extremity
1.
2.
1.
2.
Areas of weakness with some specificity for ALS
Very proximal denervation
Paraspinous
Posterior neck
Jaw weakness: Closure; Opening
Voice
Nasal, slurred speech
Continuous emission of sound
Poliomylitis
Only a small proportion of people who are exposed to poliovirus develop either minor
illness (gastroenteritis) or the major illness several days after the infection.
Major illness resembles aseptic meningitis. Approximately 50% of patient progress to
paralytic disease within 2-5 days.
Paralytic phase: localized fasciculations, severe myalgia, hyperesthesia, and usually
fulminant focal and asymmetrical paralysis.
Leg muscle involvement is more frequent, than arm, respiratory, and bulbar muscles.
Recovery may begin during fist week, but it estimated that 80% of recovery occurs in 6
months.
Further improvement may continue over the ensuing 18-24 months.
CSF: PN cells, protein is mild-to-moderately increased.
Stool culture are positive nearly in 90% of patients by the 10 th day of illness
Progressive Post Poliomyelitis Muscular Atrophy (PPMA)
In the USA ~ 250k-640k people survived acute poliomyelitis during the last epidemics in
the 1940s-1950s.
The reported incidence of PPMA ranges from 0 to 64%
PPMA includes progressive LMN syndrome, and post polio syndrome or late effect of
remote polio, chronic fatigue, orthopedic and musculoskeletal problems
Benign Focal Amyotrophy/ Hirayama's disease
Onset: Young adult; 15 to 25 years; Up to 40 years in India
Epidemiology: more than 60% are man
Male > Female: Up to 10:1
Usually sporadic
Occasional familial occurrence
Common in Eastern India
The etiology is unknown. The number of large and small motor neurons is reduced. It
may have some connection with segmental SMA.
Weakness:
Often confined to a single arm
Distal involvement (97%): C7, C8 & T1 innervated muscles; Hand & Forearm
Proximal > Distal: 10%
Side: Right = Left
Atrophy: "Oblique amyotrophy"; Sparing brachioradialis
Tremor (80%): On finger extension
Typical Hirayama syndrome
Progression: Over 1 to 5 years; Occasionally as long as 8 years
Static after progression phase: May persist for decades
Disability: Mild or none in 73%
Laboratory, EMG: Chronic denervation
In affected limb(s) (100%)
Opposite arm or lower extremities in some patients
Signs of acute denervation in 45%
NCS: Small CMAPs in affected limbs
Sympathetic skin response: May be abnormal
MRI
? Some patients with inelastic dura: Spinal cord compression with neck flexion
No major spinal anomalies
T2 signal in anterior horns of gray matter
Spinal cord atrophy: C6 & C7
Mild flexion-induced cord displacement
Spinal muscular atrophy
SMA was described independently by Werdnig and Hoffmann in 1891
Werdnig described the condition as "neurogenic dystrophy"
Hoffmann established the spinal nature of the disease
Clinical features:
Congenital SMA (5q) with arthrogryposis
Severe hypotonia
Movements: Absent; Respiratory failure at birth
Cranial nerves: Facial diplegia; ± External ophthalmoplegia
Contractures: Especially knees
Course: Death < 30 days
Pathology
Loss of motor & sensory myelinated axons
Motor neurons: Preserved, swollen
Rule out X-linked SMA
Werdnig-Hoffmann (Type 1)
Onset
Usually before 3 months
Range
0 to 6 months
Some with in utero decreased fetal movements
Acute onset in occasional patient
Weakness
Diffuse; Proximal > Distal
Severe
Poor feeding
Respiratory insufficiency: Paradoxical respirations
Sparing of facial & oculomotor
Hypotonia
Fasciculations: Tongue
Tendon reflexes: Reduced or absent
Intellect: Normal; Alert faces
Prognosis
Respiratory failure
Death: 50% by 7 months; 95% by 17 months
Chronic course in 5%
Pathology: Muscle
Large regions of grouped muscle fiber atrophy
Most larger fibers are type I
Kugelberg-Welander (Types II & III)
Classification
Type II: Intermediate
Onset: Often < 18 months
Never stand
Life span
1. Often shortened
2. Death > 2 years
Type III: Mild
Onset: Often > 18 months
Stand independently
Life span
1. ± Shortened
2. Death in adulthood
Laboratory
Serum CK: Normal
Electrophysiology
EMG: Fibrillations; Large amplitude action potentials
NCS: Small amplitude CMAPs; Mild slowing; Sensory normal
Muscle biopsy
Grouped atrophy
Type I muscle fiber predominance
Bulbo-Spinal Muscular Atrophy (Kennedy's Syndrome)
Most common adult onset SMA
General frequency: 1 in 50,000
SBMA especially common in
western Finland
Some regions in Japan
Age: Mean 27 years; Range 15 to 60 years
Early symptoms & signs: Adolescence
Muscle discomfort: Cramps or Pain
Fatigue: General; Chewing
Gynecomastia: May be asymmetric
Weakness: Not common early; May be distal
Symptoms at 30 years
Lower > Upper limb weakness
Occasionally cramps
Progressive muscular atrophy
Widespread Lower Motor Neuron Syndrome
Weakness: Distribution
Distal & Proximal: Either may be more prominent
Asymmetric
Often involves paraspinous & respiratory muscles
Often spares bulbar musculature
Spontaneous motor activity
Cramps: Common in legs, at night
Fasciculations
No upper motor neuron signs
Pain: Related to immobility
Time course
Progressive
Similar to, more rapid, or slower than, typical ALS
Muscle pathology: Grouped atrophy > Fiber type grouping
No serum antibodies
No conduction block
No evidence for response to treatment
Pathology:
Loss of motor neurons in anterior horn of spinal cord
Shrinkage of remaining motor neurons
Thank You