A MasterClass on this clinical condition will be released soon.
That’s why I wanted to give you some insights to understand this phenomenon, which is so common and so poorly understood.
It is undeniable. To have a toe-walking pattern, an increased extensor tone is necessary. The muscle or the short myotendinous unit will be the consequence, as I understand it. You cannot say that shortening came first and then tone, but rather the opposite.
The question is, what could have caused the extensor tone to increase? I would like to analyze the different neurological tracts that may influence extensor tone and whose analysis could lead to a better factorial analysis in children with toe-walking gait.
The muscle tone in the lower limbs is mainly regulated by a balance between excitatory and inhibitory tracts that travel through the spinal cord, with a special relationship to the gamma circuits that innervate intrafusal fibers.
The main spinal tracts are the corticospinal, reticulospinal, and vestibulospinal tracts, but there are others that are not as well known.
These tracts integrate sensory, motor, and postural information to maintain proper posture and movement. However, if they are damaged or altered, they may result in increased extensor tone (either spastic or not) and a toe-walking gait.
🔹 1. Corticospinal (pyramidal) tract
- Origin: Primary motor cortex
- Function:
- Fine and precise voluntary control.
- Damage: Causes spastic hypertonia, predominantly extensor in the lower limbs.
- Analysis: This is the inhibitory tract affected in brain damage, leading to a spastic pattern associated with toe-walking. However, its characteristics are clearly distinct from idiopathic toe-walking or toe-walking observed in autism.
🔹 2. Reticulospinal tract
- Origin: Reticular formation (pons and medulla oblongata).
- Divisions:
- Pontine reticulospinal (medial): Facilitates extensor tone.
- Bulbar reticulospinal (lateral): Inhibits extensor tone.
- Function:
- Modulates postural reflexes.
- Participates in the automatic control of tone.
- Importance: The balance between both parts determines whether the tone increases or decreases.
- Analysis: this tract may be affected in children whose extensor pattern increases when they are excited or stressed or who present central sensorimotor alterations observed in balance or coordination problems, among others. These are usually children with neurodevelopmental disorders (e.g., autism, Asperger’s, etc.). But… Could it play a role in toe-walking in some children with neurodevelopmental disorders, even if their diagnosis is not entirely clear?
🔹 3. Vestibulospinal tract
- Origin: Vestibular nuclei (mainly lateral).
- Pathway: Descends ipsilaterally through the spinal cord.
- Function:
- Facilitates the contraction of antigravity extensor muscles.
- Maintains posture and balance in response to signals from the inner ear.
- Damage or Hyperfunction: Can contribute to an increase in extensor tone.
- Analysis: this tract might cause increased extensor tone in the lower limbs in children with cervical dysfunctions or poor vestibular programming, which may be associated with toe-walking. Could it be one of the tracts affected in cases of excessive neuromeningeal tension?
The tectospinal tract from the superior colliculus and the rubrospinal tract from the red nucleus do not have as much responsibility for extension patterns in the lower limbs.
🔹 4. Other tracts:
There are other tracts that are not as well known or described but still have an influence on extensor tone.
- Olivospinal tract: Originates from the inferior olivary nucleus, very little studied in humans and controversial. It may modulate muscle reflexes.
- Descending propriospinal tracts: Arise from cervicothoracic interneurons, coordinating intersegmental movements and automatic postural responses.
Conclusions
Toe-walking does not start with a short muscle but rather with an increase in extensor tone in the lower limbs.
Understanding the tracts that may lead to this increased tone allows for targeted evaluation and specific intervention addressing the associated factors.
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