Sensorimotor Impairment in Neck Pain

Original Editor - Tarina van der Stockt

Top Contributors - Tarina van der Stockt, Kim Jackson, Jess Bell, Lauren Lopez, Robin Tacchetti, Ewa Jaraczewska, Wendy Walker, Simisola Ajeyalemi, Rucha Gadgil and Jorge Rodríguez Palomino

Introduction

Neck pain is a multifactorial condition, influenced by psychological, social, biological and behavioural factors.^[1] Research shows that impaired cervical proprioception is commonly associated with neck pain, leading to cervical sensorimotor control disturbances.^[2]^[3]^[4] The proprioceptive system in the cervical spine plays a crucial role in controlling balance and posture.^[5]

Sensorimotor Function

The cervical spine has numerous mechanoreceptors responsible for proprioceptive input. These receptors have central and reflex connections to the vestibular and visual systems and the central nervous system.^[6] Mechanoreceptor input from the upper cervical region enables coordination between vision and neck movement.^[7] The suboccipital area has a particularly high density of muscle spindles, making this region especially important for sensorimotor control.^[6]

Three reflexes influence sensorimotor control:^[7]

Cervicocollic reflex^[7]
- works with the vestibulocollic reflex
- leads to neck muscle activation
- prevents excessive neck rotation
Cervico-ocular reflex^[7]
- works with the vestibulo-ocular and optokinetic reflexes
- controls the extraocular muscles
- responsible for clear vision when moving the head
Tonic neck reflex^[7]
- integrated with the vestibulospinal reflex
- helps maintain a stable head position during movement of the body by modulating muscle activity in the limbs

Sensorimotor Impairment

The cervical receptors can become dysfunctional following neck trauma, such as a whiplash injury.^[6] Receptor sensitivity is affected by chemical changes, such as inflammation. Pain and psychosocial stress can also alter muscle spindle sensitivity.^[7] Impairments and changes within the neck muscles (e.g., atrophy, degeneration, fatty infiltration, fatigue) affect the cervical afferent input by changing proprioception, joint mechanics and the sensitivity of the muscle spindles.^[7] Dysfunction of the cervical receptors affects the “integration, timing, and tuning of sensorimotor control."^[6]

More sensorimotor dysfunction occurs with injury to the upper cervical region than the lower cervical region because the upper region contains more muscle spindles, has a greater connection to the visual and vestibular systems, and has more reflex activity.^[7] ^[8]

Postural stability changes happen because of changes in the sensory input between the upper cervical spine and the vestibular structures. As a result, the patient’s vestibular structures are unable to distinguish between accurate and inaccurate information. This results in a sensory mismatch that leads to feelings of dizziness or unsteadiness. Patients with neck pain may have an increase in muscle activity or stiffness as the body tries to compensate for a loss of balance.^[7]

With chronic whiplash associated disorder (WAD), more than 70 percent of patients report dizziness and 50 percent report visual and balance disturbances,^[9] even though they do not have any vestibular problems.^[10]

Sensorimotor impairment can be conceptualised as having three pillars: proprioceptive (proprioception), visual (eye movement control), and vestibular (balance and postural stability).^[11] Research has not found any association between these three pillars and medication use, age, anxiety, or compensation status.^[10]

Symptoms of Sensorimotor Impairment

Changes in sensorimotor control in patients with neck pain can lead to a range of symptoms, including an altered sense of cervical joint position (proprioception), changes in eye movement control, and changes in postural stability. Patients may experience subtle dizziness/unsteadiness, feeling lightheaded, or a feeling of spinning in the head (not the surroundings spinning like with vertigo). Some patients report poor head-neck posture awareness (feeling that their head "wobbles") or visual disturbances such as blurry vision, a smaller visual field, seeing grey spots, temporary blindness, photophobia, and vision impairments. Some patients with neck pain have difficulty reading.^[6]^[7]^[12]

Subjective symptoms are more prominent early in the day when the patient’s neck is stiff, and later during the day when the muscles are fatigued.^[7] Symptoms may also be provoked by quick head movements, watching a moving object, or walking in the dark.^[7]

Tests

Proprioception

Cervical joint position error (JPE)^[13] is considered a primary measure of mismatched cervical afferent input leading to abnormalities with sensorimotor control.^[10] It is often positive in patients with whiplash.^[10]

To perform this test, a laser pointer is fixed to a headband. The patient sits 90-100 cm away from a wall. The patient's head starts in neutral. The patient then closes their eyes, rotates their head, and returns to neutral. The examiner measures the average difference between the start and end position after three attempts to each side. A difference of more than 6.5 cm indicates dysfunction (positive test), while normal values are approximately 3-5 cm. Patients may have jerky movements, “search” for the correct position, or overshoot (a sign of an altered cervicocollic reflex). Some patients may complain of feelings of dizziness or unsteadiness during the test^[7]^[14]

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Eye Movement Control

Smooth Pursuit Test

The Smooth Pursuit Test assesses eye movement control during target tracking with the head and trunk in neutral. Results are then compared to performance when the trunk is rotated.^[7]^[16]

The patient is sitting. An object (e.g., a pen) is moved slowly from side to side in front of the patient. The patient follows the object with their eyes only. Signs to observe include quick saccadic eye movements (where it looks like the eye is trying to catch up with the object, especially in mid-range) and reproduction of the patient’s symptoms, such as dizziness or blurry vision.^[7]

Smooth Pursuit Neck Torsion Test

The Smooth Pursuit Neck Torsion Test (SPNT) monitors eye movements during target tracking with the head neutral and then with the body rotated 45 degrees under the head in either direction.^[10]^[17] A positive test shows a change in eye movement control with trunk rotation, specifically an increase in saccadic eye movements. This may be seen in patients with neck pain due to whiplash.^[7] If the patient performs poorly on the initial smooth pursuit test and this does not change with trunk rotation, a CNS disorder is more likely than sensorimotor impairment.^[7]

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Gaze Stability

In this test, the patient moves their head while focusing on an object. The patient sits looking at a point straight ahead and keeps looking at this point while turning their head left and right, or up and down (flexion and extension). Patients with neck pain may have difficulty keeping their eyes fixed on a point, and often demonstrate reduced speed or range of movement (<45 degrees).^[7]

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Balance and Postural Stability

Patients often don’t realise their balance is affected until it is tested.^[7] Useful balance tests include bilateral stance (comfortable and narrow standing with eyes open and closed for 30 seconds, first on a firm surface and then on a soft surface, such as 10 cm foam) and tandem and single limb stance (on a firm surface, with eyes open and closed, holding for 30 seconds). Note that tandem stance is commonly impaired in people 45 years of age and older.^[10]^[7]

Positive findings include a large sway in a comfortable stance, difficulty correcting or preventing sway (signs of rigidity), and maintaining stance for less than 30 seconds. Changes in the cervical afferent input might be responsible for the sway people have in comfortable stance after a whiplash injury.^[7]^[10]

Differentiation

Peripheral Vestibular Damage

Peripheral vestibular damage^[10] includes benign paroxysmal positional vertigo, damage to the endolymphatic sac, or a perilymph fistula.^[22] Approximately 35% of patients who have neck pain due to a high-force incident may have vestibular damage.^[22] The SPNT test differentiates between vestibular pathology and cervical afferent dysfunction due to neck pain. Coordination between cervical and vestibular input is required for the brainstem to determine head position in space. In peripheral vestibular pathology, patients tend to have more difficulty with challenging positions, such as narrow stance on a soft surface with eyes closed. There is also pronounced vertigo.

Acoustic Neuroma

In acoustic neuroma, the SPNT test is negative. Patients have more disturbances in postural stability when standing on a soft surface with a narrow base of support with eyes closed, but are more stable in comfortable stance positions than someone with neck pain and sensorimotor impairment. Symptoms, such as tinnitus, blurry vision, confusion and loss of hearing, are exacerbated when walking in crowded places, making sudden movements, or feeling stressed.^[10]

Vertebrobasilar Insufficiency/Cervical Arterial Dysfunction

Vertebrobasilar insufficiency/cervical arterial dysfunction should be ruled out. Patients may complain of double vision, which is not typically seen with somatosensory disturbances.^[7] Vertebral artery dissection is rare but should always be considered when assessing a patient with sensorimotor changes, particularly if they present with severe neck pain and headache on one side and have "transient or ongoing specific neurological dysfunction".^[22]

Central Nervous System Disorder

In central nervous system (CNS) disorders, symptoms remain unchanged when doing the SPNT test. A CNS disorder should be considered if the patient has sustained a direct blow to the head.^[22]

Benign Paroxysmal Positional Vertigo

In benign paroxysmal positional vertigo (BPPV), symptoms are episodic and triggered by changes in head position, such as moving in bed or bending over. Vertigo and dizziness typically last one minute or less.

Other Considerations

Anxiety, medication and stress should also be considered in the differential diagnosis
Any CNS signs or symptoms without a clear cause are red flags, and the patient should be referred to a medical doctor^[7]

For more information on specific tests for differentiation, please see page 6 of this journal article.

General Management

In patients with minimal sensorimotor impairment, conventional management might be sufficient.^[10]

Specific treatments include:

Manipulative therapy: improves dizziness and cervical proprioception
Training focusing on neuromuscular control: improves cervical proprioception
Cervical muscle endurance training: improves balance
Acupuncture: improves balance and cervical proprioception
Gaze stability, proprioception and eye-neck coordination training: improves sensorimotor deficit, range of motion, neck pain and disability
Vestibular rehabilitation: can improve balance problems and dizziness in patients with whiplash
Balance retraining
Trigger point therapy
Range of motion and neck proprioception exercises
PNF
Deep neck flexor strengthening^[7]

These treatments alone cannot improve all the sensorimotor dysfunctions. Patients with significant sensorimotor impairments with neck pain need focused management of the affected areas to help manage symptoms and avoid relapse.^[10] Combined approaches have been shown to work best for these patients.^[7]

Specific Sensorimotor Control Intervention

Sensorimotor training (SMT) protocols, which include proprioceptive, eye-cervical, tactile, and visuomotor exercises, aim to correct sensorimotor deficits. These protocols focus on joint proprioception, oculomotor control, and balance.^[23]

The programme should be tailored to each patient's presenting symptoms.^[7] Patients should not experience an increase in pain or headache; if this happens, exercises should be made less challenging and performed in a more supported position, like lying. During vestibular exercises, patients may experience a temporary increase in symptoms, such as nausea, subtle dizziness/unsteadiness, or visual disturbances.

Exercises should be performed 1-2 times per day, starting with 3-5 repetitions and progressing to 10. Patients should start in an easier, stable position and at a speed that allows precise movement. Range and speed should be increased as the patient improves, progressing to softer surfaces or more difficult positions, such as tandem stance.

General Guidelines

Work on the aspects that provoke dizziness, starting with slow, small movements and progressing gradually
Start in a seated position, progressing to standing, tandem standing and walking
Progress exercise duration from 30 seconds 2 times per day, to 1-2 minutes 3 times per day, and up to 5 minutes 5 times per day
Vision should be unrestricted initially, before progressing to restricted peripheral vision
When practising eye movement or gaze stability, start with a dot, then a word, then a business card^[24]

Proprioception/ Cervical Joint Position Error (JPE) ^[7]

The patient sits in front of a wall with a laser pointer fixed to a headband (as in the assessment). The patient brings their head back to neutral from any direction, such as rotation or extension. Training should focus on the most difficult or symptomatic direction by rotating towards or from the impaired side. The patient starts with their eyes open. They then progress to eyes closed, but open their eyes to check their position. Progressions include stopping at certain intervals, such as 20 degrees or 40 degrees, performing the exercise in different standing positions, and tracing a figure-of-eight with the laser.

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