193. Motor Neuron Diseases

Question 1

What are upper motor neurons (UMNs)?

Answer 1

UMNs originate in the primary motor cortex and have axons that form the corticospinal and corticobulbar tracts.

Question 2

What are the signs of upper motor neuron disorders?

Answer 2

Weakness, hyperreflexia, and spasticity.

Question 3

Where do lower motor neurons (LMNs) originate?

Answer 3

In the motor nuclei of the brainstem and anterior horn of the spinal cord.

Question 4

What are the signs of lower motor neuron disorders?

Answer 4

Weakness, atrophy, fasciculations, and muscle cramps.

Question 5

What is amyotrophic lateral sclerosis (ALS)?

Answer 5

The most common form of motor neuron disease, a fatal, progressive neurodegenerative disorder affecting neurons in the corticospinal tracts and anterior horn of the spinal cord.

Question 6

At what age is ALS typically diagnosed?

Answer 6

In the third to fifth decade of life.

Question 7

What is the median survival time for ALS patients?

Answer 7

3 to 5 years.

Question 8

What are the classic presentations of ALS?

Answer 8

Asymmetric limb weakness, fasciculations, and muscle atrophy.

Question 9

What bulbar symptoms are associated with ALS?

Answer 9

Dysphagia and dysarthria.

Question 10

What is pseudobulbar affect?

Answer 10

Inappropriate laughing, crying, or yawning.

Question 11

What extrapyramidal features may occur in ALS?

Answer 11

Facial masking, tremor, bradykinesia, and postural instability.

Question 12

What cognitive deficits can be associated with ALS?

Answer 12

Deficits in executive function and language.

Question 13

What behavior changes are observed in ALS patients?

Answer 13

Apathy, disinhibition, and perseveration.

Question 14

What autonomic symptoms may occur in advanced ALS?

Answer 14

Diaphoresis, impaired gastrointestinal motility, urinary urgency, and sympathetic hyperactivity.

Question 15

What is primary lateral sclerosis (PLS)?

Answer 15

A rare progressive disease characterized by UMN symptoms of weakness, gait changes, spasticity, and hyperreflexia.

Question 16

How does PLS differ from ALS in terms of progression?

Answer 16

PLS has slower progression and longer survival than ALS.

Question 17

What is hereditary spastic paraplegia (HSP)?

Answer 17

A genetically heterogenous disease resulting in progressive degeneration of the corticospinal tract.

Question 18

How can HSP be inherited?

Answer 18

Autosomal dominant, autosomal recessive, or X-linked patterns.

Question 19

What are common symptoms of hereditary spastic paraplegia?

Answer 19

Leg weakness, spasticity, and bladder dysfunction.

Question 20

What is progressive bulbar palsy (PBP)?

Answer 20

A progressive degenerative UMN and LMN disorder affecting the motor nuclei of the medulla.

Question 21

What initial symptoms are associated with PBP?

Answer 21

Atrophy and fasciculations of the lingual muscles, dysarthria, and dysphagia.

Question 22

What is spinal muscular atrophy (SMA)?

Answer 22

A group of degenerative disorders of the α-motor neurons in the anterior horn of the spinal cord.

Question 23

What causes spinal muscular atrophy?

Answer 23

A protein (SNM) deficiency due to a chromosomal mutation of the SMN1 gene on chromosome 5.

Question 24

What are the four phenotypic groupings of SMA based on age of onset?

Answer 24

• Type I: Werdnig-Hoffman disease (<6 months) * Type II: Dubowitz disease (3–15 months) * Type III: Kugelberg-Welander disease (18 months–adulthood) * Type IV (>30 years)

Question 25

What is spinobulbar muscular atrophy (SBMA)?

Answer 25

An X-linked disorder characterized by progressive weakness and atrophy.

Question 26

What genetic mutation causes SBMA?

Answer 26

An unstable CAG expansion repeat on the androgen gene of chromosome Xq11-12.

Question 27

What anesthetic considerations are important for patients with motor neuron disease?

Answer 27

Preoperative assessment of skeletal and respiratory muscle strength, avoiding general anesthesia if possible.

Question 28

What is a common surgical procedure for advanced ALS patients?

Answer 28

Tracheostomy to facilitate ventilatory support.

Question 29

What should be monitored postoperatively in motor neuron disease patients?

Answer 29

Respiratory insufficiency.

Question 30

What pain management considerations are there for patients with ALS postoperatively?

Answer 30

Increased risk for significant postoperative pain due to reduced mobility and preexisting muscle cramps and spasticity.