The syndrome of peripheral motor neurone (lower, alpha-motor neurone)


The damage is at the level of the alpha motor neurone and lower.

The basic features of each level of peripheral lesions are shown in Fig. 1.


Fig. 1

Lower motor neuron                       muscle weakness and fasciculation in the area by the range
of lesion



Roots                                     muscle weakness and fasciculation in area radicularis

                                               lesion of sensation in area radicularis



Nerve                                     muscle weakness and eventually lesion or sensation in
area nervina



Neuromuscular junction                muscle fatigue without sensory disturbances



Muscle                                              muscle fatigue without sensory disturbances




Note 1

Area nervina – area of one nerve supply
Area radicularis - area of one root supply



The clinical manifestations - general

Within the peripheral system, symptoms can vary depending on which part of the periphery is
affected predominantly. It is understood that general manifestations of peripheral impairment are
usually present (see Tab. 1).

















           Tab. 1.  The basic difference between the peripheral and central disabilities

                                             Parameter

                                      The peripheral lesions

  Central lesions (with predominant impairment of pyramidal pathways after remission of the acute
                                              stage)

The proprioceptive reflexes

Decreased or absent

Increased

The muscle tone

Decreased (flaccid paresis)

Increased (spasticity)

The pyramidal irritative phenomena (Spastic signs)

Absent

Present

The sensitivity disturbances

If they are present, so in the corresponding distribution (area nervinae, radiculares or with
distal maximum)

If they are present, they are extensive, whole limbs

The muscle atrophy

Yes, from an early stage in the respective distribution

Only in the late stages

Twitching (fasciculation)

Yes

No

Muscle weakness

In the respective distribution

In the respective distribution


The clinical manifestations - of each level of peripheral lesions

Damage of muscle

• muscle weakness (location depends on the distribution of disability)
• atrophy, hypertrophy, pseudohypertrophy (replacement of dysfunctional muscle tissue in some types
of muscular dystrophy)
• hypotonia
• reduced (but may be normal) proprioceptive reflexes
• no sensory loss, but it can be a pain (myositis, rhambdomyolysis)


Disability of the neuromuscular junction

• muscular fatigue, weakness, depending on the previous exercise
• no sensory loss
• no pain
• normal muscle tone
• normal proprioceptive reflexes
• normal muscle trophic


Affection of the peripheral nerves
• muscle weakness, hypotonia and hyporeflexia, hypotrophy of muscles (peripheral "weak" paresis) in
the distribution area nervina with prolonged condition
• sensory loss in the distribution area nervina or in "glove, sock distribution” (not always
present, depending on whether the affected nerve has a sensitive component)
• can be a pain


Affection of plexus
• Muscle weakness, hypotonia and other manifestations of weak paresis

·           sensory disturbances in the distribution of inadequate area nervina or radicularis (is
the larger, plurisegmental)


Affection of roots
Affection of posterior root
• sensory loss and possibly pain in the distribution area radicularis
• decreased the proprioceptive reflexes (if not compensated by the neighboring roots supplying the
same muscle)
• no weakness
• not muscle twitching


Affection of front root
• muscle weakness, hypotonia and other manifestations of weak paresis in the distribution area
radicularis
• muscle twitching
• no sensory loss
• no pain


At the root disability are usually combined handicap of posterior and of front root.


Affection of lower motor neuron
• muscular weakness, hypotonia and other manifestations of flaccid paresis in the area
corresponding of the range of affected anterior horn cell may not match the area radicularis
• otherwise identical finding as the of front disability root