Assessment of Motor Neuron Disease

Assessment of Motor Neuron Disease

• Motor Neuron Disease (MND) is a degenerative disease with a gradual onset and progressive course, affecting only the motor system.
• The typical age of onset is middle to old age, with males more frequently affected than females.
• The course of the disease is gradual and progressive.
• Symptoms are usually bilateral and depend on the affected area.

Types of Motor Neuron Affection

• Upper Motor Neuron (UMN) affection:

  • In the spinal cord, UMN affection can cause bilateral symptoms, potentially leading to spastic paraplegia (below the cervical region) or spastic quadriplegia (at the level of the cervical region).
  • In the brain stem or cerebral hemisphere, affected individuals experience pseudo-bulbar palsy symptoms, including bulbar symptoms, quadriplegia, exaggerated palatal and pharyngeal reflexes, emotional and mood changes, and an exaggerated jaw reflex (if the lesion is above the pons).

• Lower Motor Neuron (LMN) affection:

  • LMN affection can occur in the spinal cord or cranial nerve nuclei of the brain stem, resulting in progressive muscular atrophy.
  • Symptoms include muscle wasting, hypotonia (decreased muscle tone), weakness, hyporeflexia (reduced reflexes), and fasciculations (muscle twitching).
  • Symptoms initially appear in the upper limbs, later progressing to the lower limbs.
  • In the Cranial nerve nuclei, true bulbar palsy can emerge, characterized by bulbar symptoms, absent palatal and pharyngeal reflexes, and wasted tongue with fasciculations.

• Combined UMN and LMN affection:

  • Also known as Amyotrophic Lateral Sclerosis (ALS), this involves a combination of UMN and LMN symptoms.
  • In the upper limb, combined affection presents as weakness, wasting, and fasciculations (LMN), along with hypertonia and hyperreflexia (UMN). This combination is often referred to as tonic atrophy.
  • In the lower limb, weakness with UMN signs is found.

Diagnosis of Motor Neuron Disease (MND)

• Nerve conduction studies: These show preservation of sensory responses, with normal or reduced motor amplitudes.
• Needle EMG: Demonstrates active denervation, shown by fibrillation potentials and chronic sharp waves in multiple myotomes.
• MRI (Brain/Spine): Shows hyperintensity in corticospinal tracts (specifically the posterior limb of the internal capsule and centrum semiovale).

Assessment of MND

• History: Includes personal information (name, age, sex, habits, onset, course, duration of symptoms, medications, past medical history, trauma, family history, and chief complaints).

• Examination:

  • General: Assess respiration, neurological status
  • Non-essential: Mental status (emotional liability, mood changes, and pseudo-bulbar palsy), evaluation of cranial nerves (all except 1, 2, 8, ocular nerves, sensory parts of V and VII); assess speech for dysarthria and dysphonia (bulbar symptoms).
  • Essential: Sensory examination is normal, Motor examination includes inspection (muscle wasting, fasciculations), assessment of muscle tone (hypertonia in UMN, hypotonia in LMN).

• *Muscle testing: Patients may fatigue easily, therefore, appropriate tests (group or functional) may be used, dependent on the level of severity.

• Reflexes: Reflex assessment is performed based on the type of affection.

• Coordination: Postural stability, reactive, anticipatory, and adaptive postural controls are assessed. ALS-specific balance tests are not available. Various general balance tests (Berg Balance Scale, Timed Up and Go Test, Functional Reach Test) are employed.

• Gait: Examination looks at the duration of gait (within time period/distance), stability, safety, endurance, energy expenditure, practicality, and ease of use of assistive devices.

• Cognition: Assess executive function, language comprehension, memory, and abstract reasoning. Common co-morbidities like depression and anxiety are screened for.

• Sensory Examination: General sensory examination is usually normal.

• Bulbar evaluation: Assessment of cranial nerves V, VII, IX, X, and XII assesses the extent of bulbar involvement (important for swallowing and speech).

• Respiratory function: Examine respiratory symptoms, breathing pattern, chest expansion, respiratory sounds, cough effectiveness, Forced Vital Capacity (FVC), and maximal inspiratory pressure (MIP) using spirometry.

• Integument: Skin integrity is usually not an issue.

• Environmental assessment: Focuses on energy conservation, safety, and current/future functional capabilities.

• Additional assessment: The Fatigue Severity Scale and other scales or measures may be used across various stages of ALS, for different functional issues.

Stages of ALS

• Stage 1 (Mild): Recent diagnosis, functionally independent in ambulation, ADLs, and speech.
• Stage 2 (Moderate): Mild deficits in function in one or more regions. Moderate to severe deficit in one region with mild/normal function in others.
• Stage 3 (Severe): Need for assistance in two or more regions (e.g., walking, transferring, upper extremity activities, dysarthria/dysphagia).
• Stage 4 (Very Severe): Nonfunctional movement in two or more regions, nonfunctional impairment in a third region.
• Stage 5 (Terminal): Death.