PRELIMS: Assessment of PNS diseases

Question 1

Progressive, symmetrical weakness of the limbs associated with diminished or absent reflexes. Maximal weakness occurs within 2 to 4 weeks.

Answer 1

Guillain-Barré Syndrome (GBS)

Question 2

Purely axonal form of GBS, leading to nerve conduction failure, with marked weakness of the oropharyngeal, neck, and shoulder muscles. Most common in Asia.

Answer 2

Acute Motor Axonal Neuropathy (AMAN)

Question 2

Affects both motor and sensory nerves and accounts for 95% of GBS cases in Europe and North America.

Answer 2

Acute Demyelinating Polyradiculoneuropathy (AIDP)

Question 2

Axonal form of GBS with pronounced sensory symptoms. More common in Asia and South America.

Answer 2

Acute Motor and Sensory Axonal Neuropathy (AMSAN)

Question 3

Immune injury occurs specifically at the myelin sheath, leading to vesicular degeneration. Most common subtype in Europe and North America.

Answer 3

Acute Inflammatory Demyelinating Polyneuropathy (AIDP)

Question 3

Characterized by ataxia, areflexia, and ophthalmoplegia, often involving cranial nerves III, IV, and VI. Accounts for 5% of cases in Western countries.

Answer 3

Miller Fisher Variant

Question 3

Predicts likelihood of walking independently at 6 months. Calculated by adding points for age and diarrhea to the GBS disability score.

Answer 3

Erasmus Guillain-Barré Syndrome Outcome Score - Prognosis

Question 3

Required Clinical Feature for GBS Diagnosis

Answer 3

Progressive Weakness in Both Arms and Legs

Question 4

Most common form of polio infection

Answer 4

Asymptomatic Infection

Question 4

Symptoms include gastrointestinal issues, flu-like symptoms, and muscle pain

Answer 4

Nonparalytic Infection

Question 4

Begins with flu-like symptoms and progresses to asymmetric paresis and paralysis

Answer 4

Paralytic Infection

Question 4

Characterized by rapid muscle atrophy due to Wallerian degeneration

Answer 4

Result of anterior horn cell involvement in Paralytic Polio

Question 4

Outcome where 30% of individuals recovered fully

Answer 4

Recovery and Residual Effects of Polio

Question 5

Outcome with 10% mortality due to respiratory involvement

Answer 5

Outcomes of Paralytic Polio

Question 5

Postpolio Syndrome (PPS) arises how many years after the initial polio episode?

Answer 5

Approximately 25 years

Question 6

Common symptoms of Postpolio Syndrome (PPS)

Answer 6

Weakness, declines in functional mobility, fatigue

Question 6

Features of Lower Motor Neuron (LMN) injury

Answer 6

Focal atrophy, muscle weakness, fasciculations

Question 6

Upper Motor Neuron (UMN) injury features

Answer 6

Spasticity, clumsiness, increased muscle stretch reflexes, UMN signs (e.g., Hoffmann sign, Babinski sign)

Question 7

Clinical significance of fasciculations

Answer 7

Suggestive of MND when accompanied by weakness and denervation; isolated fasciculations not pathognomonic

Question 7

Examining for fasciculations and their diagnostic importance

Answer 7

Fasciculations with weakness and EMG findings of denervation are strongly suggestive of MND

Question 7

What is the hallmark characteristic of Amyotrophic Lateral Sclerosis (ALS)?

Answer 7

Progressive degeneration of both Upper Motor Neurons (UMN) and Lower Motor Neurons (LMN).

Question 7

What are the key clinical manifestations related to Upper Motor Neuron (UMN) pathology in ALS?

Answer 7

Initial: Spasticity, dysnergia, abnormal timing, loss of dexterity, fatigue, gait difficulties, decreased balance, hyperreflexia, clonus, pathological reflexes (e.g., Babinski, Hoffman)
Progression: UMN signs may decrease.

Question 7

What are the common symptoms of Lower Motor Neuron (LMN) pathology in ALS?

Answer 7

Muscle weakness, typically starting distally (hands and feet)
Secondary impairments: decreased ROM, joint subluxation, tendon shortening, contractures, ambulation difficulties, impaired postural control
Common symptoms include foot drop, falls, and fasciculations.

Question 8

Describe the different types of Bulbar palsy in ALS and their associated symptoms.

Answer 8

Spastic Bulbar Palsy: Forced or strained voice, difficulty with speech.
Flaccid Bulbar Palsy: Hoarse, soft, or breathy voice, impaired swallowing, risk of aspiration.
Mixed Palsy: Combination of spastic and flaccid symptoms.

Question 9

What are the respiratory impairments seen in ALS?

Answer 9

Weakening of respiratory muscles leading to reduced vital capacity (VC)
Symptoms: Fatigue, dyspnea, difficulty sleeping supine, morning headaches, excessive daytime sleepiness.
Progression: Linear decline, with VC reduction indicating a high risk of respiratory failure.

Question 9

What cognitive impairments are associated with ALS?

Answer 9

Affects frontotemporal pathways
Symptoms: Verbal fluency issues, language comprehension problems, memory issues, abstract reasoning difficulties, overall cognitive decline.
More common in bulbar-onset ALS.

Question 9

What are the key features of the El Escorial Criteria for diagnosing ALS?

Answer 9

Diagnosis should include both UMN and LMN degeneration
Different levels of diagnostic certainty based on regional spread (cranial, cervical, thoracic, lumbosacral).

Question 10

How does the Awaji Criteria differ from the El Escorial Criteria in diagnosing ALS?

Answer 10

Incorporates neurophysiological evidence (fasciculation potentials)
Emphasizes EMG changes in two muscles in cervical or lumbar segments
Shows increased sensitivity for early diagnosis and bulbar-onset ALS.

Question 10

What is the focus of the Gold Coast Criteria?

Answer 10

Specifically used for diagnosing Guillain-Barré Syndrome (GBS), not ALS
Evaluates patterns of muscle weakness, sensory changes, and other symptom characteristics in GBS.

Question 10

What are the common cranial nerves affected in ALS?

Answer 10

CN V (Trigeminal)
CN VII (Facial)
CN IX (Glossopharyngeal)
CN X (Vagus)
CN XI (Spinal Accessory)
CN XII (Hypoglossal)

Question 11

What is the primary pathophysiology of Myasthenia Gravis?

Answer 11

Autoimmune disorder affecting postsynaptic neuromuscular transmission, with antibodies targeting nicotinic acetylcholine receptors (nAChR) at the neuromuscular junction, leading to reduced receptor function and muscle weakness.

Question 12

What are the common initial symptoms of Myasthenia Gravis?

Answer 12

Ptosis (drooping eyelids) and diplopia (double vision). Other symptoms include limb weakness, difficulty chewing, swallowing, or talking.

Question 12

How does Myasthenia Gravis commonly progress?

Answer 12

It often starts with ocular symptoms and can progress to generalized muscle weakness affecting facial, bulbar, truncal, and limb muscles. Most patients develop generalized disease within 13 months of onset.

Question 13

What are the classifications of Myasthenia Gravis according to the MGFA Clinical Classification?

Answer 13

Class I: Ocular muscle weakness with normal strength in other muscles.
Class II: Mild weakness affecting non-ocular muscles, with subcategories IIa (limb/axial) and IIb (oropharyngeal/respiratory).
Class III: Moderate weakness, with subcategories IIIa (limb/axial) and IIIb (oropharyngeal/respiratory).
Class IV: Severe weakness, with subcategories IVa (limb/axial) and IVb (oropharyngeal/respiratory).
Class V: Need for intubation with or without mechanical ventilation.

Question 13

What is a myasthenic crisis?

Answer 13

A severe form of Myasthenia Gravis characterized by life-threatening muscle weakness, particularly affecting bulbar and respiratory muscles. It requires intensive care and can be the first presentation in approximately 20% of patients.

Question 14

What are the primary diagnostic tools for Myasthenia Gravis?

Answer 14

Clinical Diagnosis: Based on history and physical examination.
Serologic Testing: Anti-Acetylcholine Receptor Antibodies (AChR-Ab) and Anti-Muscle-Specific Kinase (MuSK) Antibodies.
Neurophysiological Testing: Repetitive Nerve Stimulation (RNS) and Single-Fiber EMG.
Edrophonium (Tensilon) Test: Shows strength improvement, particularly useful for ocular symptoms.

Question 14

What are the primary diagnostic tools for Lambert-Eaton Myasthenic Syndrome?

Answer 14

Electrodiagnostic Testing: Reduced motor amplitudes, RNS showing decrement and postexercise facilitation.
Serum Antibody Testing: P/Q Calcium Channel Antibodies, SOX1 Antibodies (for paraneoplastic form), Alpha-1A P/Q VGCC Domain IV Antibodies.
Imaging Studies: CT or PET scan to screen for underlying malignancy, especially SCLC.

Question 15

What are the common features of Ocular Myasthenia Gravis?

Answer 15

Affects only eyelids and extraocular muscles, often a milder initial form of the disease, and may progress to generalized Myasthenia Gravis over time.

Question 15

What is Neonatal Myasthenia Gravis?

Answer 15

Occurs in about 10% of infants born to mothers with MG due to placental transfer of AChR antibodies, with symptoms usually resolving within a few months after birth.

Question 16

What causes Lambert-Eaton Myasthenic Syndrome?

Answer 16

Antibodies directed against presynaptic voltage-gated P/Q calcium channels on motor and autonomic nerve terminals, leading to reduced calcium influx and decreased acetylcholine release.

Question 16

What is the characteristic electrodiagnostic feature of Lambert-Eaton Myasthenic Syndrome?

Answer 16

Repetitive Nerve Stimulation (RNS) shows a >10% decrement in motor amplitudes at low frequencies (2 to 5 Hz) and a >100% increment in motor amplitudes after brief exercise (postexercise facilitation).

Question 16

What are the key physical findings in Lambert-Eaton Myasthenic Syndrome?

Answer 16

Proximal muscle weakness, diminished or absent muscle stretch reflexes, and transient strength improvement after brief exercise. Autonomic dysfunction symptoms include dry mouth, sexual dysfunction, blurred vision, constipation, and orthostatic hypotension.

Question 16

What are the two main forms of Lambert-Eaton Myasthenic Syndrome?
c

Answer 16

Paraneoplastic: Often associated with small cell lung cancer (SCLC).
Nonparaneoplastic (Autoimmune): Not associated with cancer, less common.