Cervical spine Clinical anatomy & Motor control Part 1

Certainly, in the literature, there is mounting evidence of an association between chronic mechanical neck pain and altered neuromuscular control” (O’Leary, Falla & Jull., 2011, p.452).

There was a lot of research regarding deficits in the deep cervical neck flexor muscles(DCNF) – longus colli and longus capitus. Further research has investigated in the presence of motor control dysfunction throughout range of motion of cervical spine dysfunction and aimed to determine the best treatment approaches for such deficits.

Some of this changes in motor control that we hear about are:
•       Increased activity in the superficial neck flexor muscles,
•       Reduced coordination of the deep neck flexor muscles.
•       Reduced endurance in the deep neck extensors.

What are the muscles  referring to?

Global movers are involved in the generation of torque and produce a range of movement. They function in a phasic manner.When find dysfunctional there is a spasm, pain and restricted range of movement joint .Local stabilizers are the deeper muscles that control segmental control and neutral positioning of a joint. Dysfunction in the local muscles results in inhibition of function, delayed timing or recruitment deficiencies and loss of segmental control and neutral joint positioning.

There are three main groups of cervical muscles which  enable control of posture and segmental movements:

1.      The deep cervical flexors – longus colli and longus capitus.
2.      The deep neck extensors – semispinalis cervicis and multifidus.
3.      The suboccipital muscles – rectus capitus posterior major & minor, and obliquus capitus superior and inferior.

CERVICAL FLEXOR :

We are  familiar with deep neck flexors (DNF). The literature often refers to the superficial muscles which become relative stiffness in the presence of neck pain and the deep neck flexors which become dysfunction.

The  superficial flexor muscles of the cervical spine include  sternocleidomastoid(SCM) and anterior scalenes (AS):•        Sternocleidomastoid functions bilaterally to create neck flexion and  to create ipsilateral lateral flexion and contralateral rotation. The SCM is innervated by a spinal root of the accessory nerve.

Anterior scalene : it  functions to elevate the first rib, and similar to SCM it creates ipsilateral lateral flexion and contralateral rotation. The anterior scalene is innervated by C4, C5, and C6 nerve roots (Cleland, 2005).

When referring to the deep flexor muscles , we are talking about longus colli and longus capitus. The function of longus colli and longus capitus is to maintain cervical lordosis and provide segmental control (Fall, Bilenkij & Jull., 2004).

When these muscles activate they create cranio-cervical flexion (CCF) and support cervical lordosis anteriorly (Jull, Sterling, Treleavan, Falla & O’Leary., 2008).

Longus capitus is innervated by C1-3 spinal segments and longus colli from C2-6 (Cleland., 2005).

Sternocleidomastoid                        Anterior scalene

CERVICAL EXTENSORS :

The flexor group consists of SCM, AS and DNF but the extensor group is consists of a lot more muscles. There are 4 layers of cervical extensors From most superficial to deep (Schomacher & Falla., 2013, p.360-361).

Here are 4 layers of extensors muscles group

•       Layer 1: Levator scapulae and upper trapezius not only primarily considered to be muscles of the shoulder girdle but also  form a superficial layer over the cervical extensor group. Upper trapezius is innervated by a spinal root of the accessory nerve and levator scapulae from the dorsal scapula nerve (Cleland., 2005).

•       Layer 2: Splenius capitus and cervicis which acts bilaterally as an extensor and ipsilaterally to produce rotation. Splenius capitus and cervicis are innervated by dorsal rami of the middle cervical spinal nerves (Cleland., 2005).

•       Layer 3: Semispinalis capitus is primarily a cervical extensor and unilaterally to create lateral flexion. Both innervated by dorsal rami of spinal nerves (Cleland., 2005).

•       Layer 4: Semispinalis cervicis and multifidus. These are  known as the  deep cervical extensors (DNE or DCNE). Semispinalis cervicis acts a cervical extensors and multifidus as a segmental stabiliser.

They provide posterior support of cervical lordosis in relation with the deep neck flexors and prevent a forward head position (Jull, Sterling, Treleavan, Falla & O’Leary., 2008). These muscles are also innervated by dorsal rami of cervical spinal nerves (Cleland., 2005).
 
Upper trapezius                   Semispinalis capitus

Splenius capitus and cervicis

CRANIOCERVICAL EXTENSORS

These four muscles form the suboccipital muscle group and which should be  rehabilitated separately to the deep cervical extensors.

•       Rectus capitus posterior major & minor – head extension and ipsilateralbrotation
•       Obliquus capitus superior – head extension and side bending.
•       Obliquus capitus inferior – ipsilateral head-on-neck rotation.

The suboccipital muscle group is important to provide proprioception and contribute to the visual and vestibular systems. They control cranio-cervical lordosis and small head-on-neck movements. Dysfunction results into sensorimotor impairment, altered kinaesthetic sense and , oculomotor control . It can lead to cervicogenic dizziness. All of these muscles are innervated by the suboccipital nerve C1 (Cleland., 2005).

Why we are beginning with the clinical anatomy?

I think, it is clinically very important to understand which muscles lie in our hands on palpation.Their fiber direction and their innervation. Dysfunction or nerve injury can lead to changes in cervical motor control.
So that we can assess motor control with a deeper understanding of what we might expect to find, what normal and abnormal results are and what the clinical relevance of these findings are.

WHAT EVIDENCE  SAY ABOUT MOTOR CONTROL DYSFUNCTION IN THE CERVICAL MUSCLES?

NECK FLEXORS:

The author states that patients with neck pain will often display reduced muscle activation in the DCNF during the  craniocervical flexion (CCF) as well as delayed activation during postural perturbations (Schomacher & Faller., 2013). Not only do we notice that patients with neck pain have different levels of control over muscle activation patterns but they also lack endurance (Jull, O’Leary, Falla., 2008, p.529).

In regards to WAD, Jull, O’Leary & Falla (2008) found that patients display higher levels of EMG activity in SCM and AS when compared to asymptomatic controls. Other studies have shown a similar pattern, of increased activity in upper trapezius, SCM and AS in patients with chronic neck pain from both insidious and traumatic origin (Falla, Bilenkij & Jull., 2004).

There are three major questions that researchers are trying to solve in regards to flexor muscle dysfunction. One is whether these deficiencies in deep cervical neck flexor (DCNF) control and increased activation in superficial neck muscles are associated with each other. Is there a cause and effect relationship between the two?

One thing that is not clear, if the motor control impairments spontaneously resolved with the recovery of neck pain. Many studies suggest that  specific training is required to improve posture, strength and endurance (Jull, O’Leary, Falla., 2008; Jull., 2008; O’Leary, Falla, Ellior & Jull., 2009; Falla., 2004). What this research suggests that maybe the motor control deficits don’t improve at the same rate as pain. If we don’t make it a priority to assess motor control during the initial treatment sessions, we have no objective measure of whether or not exercises are required. Once pain and movement has resolved, most patients might wrongly assume they have fully recovered and convincing them to perform a home exercise program which might be difficult. HOwever, if we document changes in strength, coordination and endurance early in our treatment. This help us  to monitor changes in these aspects of recovery, then we can promote more compliance in our patients to complete their rehabilitation.

NECK EXTENSORS:

Schomacher & Falla (2013) published a paper in recent times highlighting the importance of the cervical extensor muscles.

“Patients with neck pain often display increased activation of the superficial neck extensors and delayed activity in semispinalis cervicis and multifidus” (Schomacher & Faller., 2013, p. 362). Which you could say is similar to the changes observed in the cervical flexor muscle group, where anterior scalene and sternocleidomastoid are observed to have increased activation while there is reduced activation in the deep cervical flexors.

“When changes in activation patterns occur in semispinalis cervicis it is generalised across all fascicles of the muscle, not just localised to the painful segment” (Schomacher & Faller., 2013, p. 362). Therefore if semispinalis cervicis is a cervical extender, changes may occur across the entire muscle belly that effects it’s ability to control and perform cervical extension across multiple levels. Why these changes occur, in both muscle groups remains unclear and possibly related to a variated of mechanisms (Schomacher & Faller., 2013).  These “studies have shown that patients with mechanical neck pain have deficiencies in maximal strength, endurance, precision during dynamic movement, and sustained isometric contraction, efficiency of contraction, and repositioning acuity” (O’Leary, Falla, Elliot & Jull., 2009., p. 327).

Take home message from the research :

My hope is that this provides sufficient evidence to support and justify why we need to be paying closer attention to the muscular control of the cervical spine.

•       We now know that they develop in most cases of neck pain and aren’t specific to one type of injury or pathology.

•       We don’t know how long it takes for the changes to develop but we do know that they don’t spontaneously resolve.

•       This means we need to be responsible for assessing our client’s cervical motor control, monitoring it during their recovery and ensuring that optimal motor control is restored.

New mindset when palpating or assessing a patient with neck pain. Before we learn how to perform the tests, first think about what muscles lie in the region you are palpating, which nerves involved them, and which movements these muscles contribute to.

“Sufficient evidence already exists to indicate that assessment of cervical muscle function should be routine in the clinical examination of patients with mechanical neck pain” (O’Leary, Falla, Elliot & Jull., 2009., p. 327).

REFERENCES:

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