gbs and nmd

What is Guillain-Barré syndrome (GBS) in terms of mechanism?

An acute post-infectious, immune-mediated peripheral neuropathy that commonly follows an antecedent infection.

Which GBS variant is the most common overall?

Acute inflammatory demyelinating polyradiculoneuropathy (AIDP).

Name the major clinical variants of GBS.

Demyelinating (AIDP), axonal (AMAN motor; AMSAN motor+sensory), and regional syndromes (e.g., Miller Fisher).

What are AMAN and AMSAN?

Axonal GBS variants: AMAN is primarily motor; AMSAN involves motor and sensory fibers.

What key epidemiologic rate is given for GBS?

~0.4 to 2 per 100,000 (rare).

How often is an antecedent infection associated with GBS?

About 2/3 of cases (up to ~70% cited).

Most common infectious risk factor for GBS listed in the notes?

Campylobacter jejuni.

What pathophysiologic concept explains Campylobacter-triggered GBS?

Molecular mimicry leading to autoimmune targeting of peripheral nerve components.

List other implicated infections in GBS from the notes.

CMV, EBV, and Zika (also mentioned: “other implicated infections”).

Outline the core AIDP immune sequence (high yield).

Triggering infection → autoantibodies bind myelin + complement activation → MAC on Schwann cells → myelin degeneration → macrophage-associated segmental demyelination with lymphocytic infiltration.

In AIDP, the membrane attack complex (MAC) primarily targets what cell type?

Schwann cells (via complement activation).

How do axonal variants (AMAN/AMSAN) differ immunopathologically from AIDP?

Autoantibodies activate complement at nodes of Ranvier with MAC formation, paranodal myelin detachment, macrophage recruitment, minimal lymphocytic infiltration, and later axonal degeneration.

In axonal GBS, where does MAC formation occur?

Nodes of Ranvier.

Classic weakness pattern in GBS?

Acute/subacute, ascending, symmetric flaccid weakness starting in the legs and progressing proximally.

What reflex finding is typical in GBS?

Areflexia or hyporeflexia.

Are sensory symptoms prominent in typical GBS?

Usually mild sensory symptoms; motor weakness predominates.

Name common pain features in GBS.

Neuropathic pain and generalized pain can occur despite mild sensory deficits.

Which cranial nerve involvement is highlighted for GBS?

Facial diplegia (CN VII) and bulbar symptoms affecting swallowing.

Which cranial nerves are associated with dysphagia in GBS per the notes?

CN IX, X, and XII.

What ocular motor issue can occur in GBS?

Oculomotor weakness.

Define dysautonomia in GBS clinically.

Autonomic instability causing GI dysmotility and cardiovascular/urinary abnormalities.

Give examples of autonomic symptoms in GBS from the notes.

Ileus, hypertension or hypotension, fever, tachycardia or bradycardia, urinary retention.

Most feared acute complication requiring close monitoring in GBS?

Respiratory failure.

What level of care may be indicated early in GBS management?

ICU-level care for close monitoring and ventilatory/autonomic surveillance.

Key respiratory monitoring recommendation in GBS?

Serial pulmonary function testing performed routinely.

What vital monitoring is emphasized in GBS supportive care?

Close BP, fluid status, and cardiac rhythm monitoring.

When is immunotherapy indicated in GBS (per notes)?

Symptom onset <4 weeks AND significant disease (non-ambulatory; or ambulatory with neuropathic symptoms).

When is immunotherapy NOT indicated in GBS (per notes)?

Mildly affected patients.

Standard IVIG dosing regimen for GBS given in the notes?

0.4 g/kg/day for 5 days.

Plasma exchange regimen for GBS in the notes?

Total ~12–15 L in 4–5 exchanges over 1–2 weeks.

Name allied health disciplines in the multispecialty GBS approach.

Physical therapy, occupational therapy, speech therapy, respiratory therapy/pulmonology, neurology, psychology.

What are motor neuron disorders (MNDs) broadly?

Hereditary neurodegenerative disorders with progressive motor neuron degeneration affecting UMN, LMN, or both.

In pediatrics, motor neuron disorders most often have what general cause and which neuron type predominance?

Genetic causes; most likely affect LMNs.

Approximate pediatric MND incidence listed?

~11 per 100,000 population.

Most common pediatric MND mentioned?

Spinal muscular atrophy (SMA).

Key etiologic themes for MND mutations listed?

Defects in protein homeostasis, RNA metabolism, mitochondrial dysfunction, vesicle transport dysregulation, impaired DNA repair, oxidative stress.

How does oxidative stress relate to MND per the notes?

It is implicated in neurotoxicity and disease development.

Core pathophysiology of MND affecting axons?

Motor neurons fail to maintain long axonal projections → axonal retraction → denervation of target muscles.

UMN lesion clinical triad (per notes)?

Hypertonia, hyperreflexia, and spastic weakness due to loss of supraspinal control.

LMN lesion clinical triad (per notes)?

Muscle weakness, atrophy, and fasciculations due to denervation of target muscle.

Where are UMN lesions located anatomically (per notes)?

Primary motor cortex (precentral gyrus) with tracts terminating in spinal cord/brainstem.

Where are LMN cell bodies located (per notes)?

Anterior horn cells of spinal cord and cranial nerve nuclei in the brainstem.

Which descending tracts are emphasized for UMN pathways?

Corticospinal and corticobulbar tracts (pyramidal; with extra-pyramidal involvement also noted).

SMA genetic locus mentioned?

Chromosome 5q13.

Functional milestone distinction: SMA type 1 vs type 2 vs type 3?

Type 1: onset birth–6 mo, never sits; Type 2: sits but does not stand/walk; Type 3: stands/walks but loses ability over time.

Nickname-style summary of SMA types from notes?

Type 1 “no sitters,” Type 2 “sitters,” Type 3 “walkers.”

What is Werdnig-Hoffmann disease?

SMA type 1 (severe SMA).

Pathologic basis of SMA type 1 weakness (per notes)?

Degeneration of anterior horn cells of spinal cord and brainstem → severe axial and limb weakness.

Key presenting symptoms of SMA type 1 listed?

Hypotonia/weakness; speaking/sucking/swallowing difficulty; respiratory problems.

Cardinal posture finding in SMA type 1?

“Frog-leg” posture with abducted hips due to severe hypotonia.

Chest/respiratory pattern described in SMA type 1?

Diaphragmatic breathing with bell-shaped chest.

Reflex status in SMA type 1?

Absent tendon reflexes.

Facial movement finding in SMA type 1?

Normal facial movements (facial sparing).

Cry characteristic in SMA type 1?

Weak cry.

Prognosis driver in SMA type 1?

Respiratory muscle weakness → respiratory compromise and infections.

Creatine kinase (CK) level in SMA (per notes)?

Normal (not a primary muscle destruction disorder).

Ultrasound finding sometimes described in SMA?

Increased echogenicity with muscle atrophy (hyper-echogenicity).

Needle EMG finding in SMA type 1?

Features of denervation (normal or reduced activation).

Supportive airway secretion management in SMA type 1?

Pharyngeal suction to aid breathing/airway clearance.

Orthopedic management concept in SMA type 1?

Spinal bracing due to hypotonia-related scoliosis risk.

Define SMA type 2 (intermediate) main functional limitation.

Unable to stand or walk; can sit unsupported.

Key clinical signs in SMA type 2 from notes.

Symmetric proximal leg weakness; tongue fasciculations; hand tremors; decreased/absent tendon jerks; facial muscles spared.

Common orthopedic complication in SMA type 2?

Scoliosis (often wheelchair dependence).

Cognitive status in SMA type 2?

Normal or advanced intellect.

Respiratory involvement in SMA type 2?

Variable intercostal weakness and respiratory problems; long-term prognosis depends on respiratory function.

Ultrasound “whiter areas” in SMA type 2 represent what?

Increased echogenicity from fat infiltration due to denervation and muscle atrophy.

Early SMA type 2 management to prevent scoliosis?

Early bracing; spinal braces or surgery when indicated.

Functional positioning strategy in SMA type 2?

Early standing posture using standing frames or calipers with PT/OT.

Common orthoses used in SMA type 2?

Hip, knee, ankle, or foot orthoses.

SMA type 3 is also called what?

Kugelberg-Welander syndrome (mild SMA).

Common early complaints in SMA type 3?

Difficulty running, climbing stairs, jumping; declining walking endurance.

Gait pattern described in SMA type 3?

Waddling, flat-footed, wide-based gait.

Classic bedside sign in SMA type 3?

Positive Gower’s sign.

Distribution of weakness in SMA type 3?

Proximal weakness with legs > arms.

Course of ambulation in SMA type 3?

Relatively static early but loss of walking ability often occurs during adolescence.

Life expectancy in SMA type 3 per notes?

Usually not significantly affected, though pulmonary complications can occur.

Core SMA type 3 management principle?

Encourage activity/ambulation to prolong walking; rehab/bracing once ambulation is lost; treat respiratory infections promptly.

Juvenile ALS (J-ALS): key distinguishing epidemiology?

Rare; onset in early childhood/adolescence (<25 years).

What neuronal types are affected in ALS?

Both upper and lower motor neurons.

What replaces lost motor neurons in ALS pathology (per notes)?

Gliosis (scarring).

What intracellular pathology is mentioned in ALS?

Intracellular inclusions.

What happens to the neuromuscular junction in ALS (per notes)?

It becomes destroyed → denervation and muscle fiber atrophy.

Common early clinical presentation of J-ALS?

Progressive focal weakness and fasciculations in one limb (often in the 2nd decade).

Why can spasticity occur in ALS?

Combined UMN and LMN involvement.

Reflexes in ALS can be what (per notes)?

Increased or decreased (mixed UMN/LMN signs).

Bulbar dysfunction in ALS includes what?

Dysarthria and dysphagia with difficulty controlling secretions.

Define pseudobulbar affect.

Involuntary, inappropriate laughing or crying with emotional lability triggered by minor stimuli.

Are sensory symptoms mandatory in ALS?

No; some may have sensory neuropathy (numbness/decreased sensation) but ALS is primarily motor.

Extraocular muscles and sphincters in ALS are typically what (per notes)?

Rarely involved.

Define split-hand pattern in ALS.

Weakness/atrophy of first dorsal interossei and thenar muscles with sparing of hypothenar muscles.

Define split-leg pattern in ALS.

Plantarflexion involvement with sparing of dorsiflexors.

Respiratory symptoms in ALS arise from what functional loss?

Loss of ability to cough and respiratory insufficiency.

Neuropsychiatric associations in ALS (per notes)?

Executive dysfunction/behavioral abnormalities; pseudobulbar affect as part of UMN syndrome.

Riluzole mechanism (per notes)?

NMDA receptor antagonist that reduces glutamatergic transmission/excitotoxicity.

Standard riluzole dose cited (adult dosing reference)?

50 mg twice daily.

Edaravone mechanism (per notes)?

Free radical scavenger that reduces oxidative stress and slows functional progression.

Which patients benefit most from edaravone (per notes)?

Those with early ALS.

Distal SMA / hereditary motor neuropathies: key features?

Rare, many genetic subtypes; slowly progressive; onset often in first 2 decades; predominantly motor with minor sensory abnormalities.

HMN1 type presentation (per notes)?

Symmetric juvenile-onset lower limb weakness with reduced/absent reflexes and normal sensation.

Other hereditary motor neuropathy subtype features listed.

UE>LE involvement, vocal cord paralysis, diaphragm weakness, pyramidal signs.