Research Roundup: October 2020

 

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Migraine: Musculoskeletal and Balance Dysfunction

Carvalho, Gabriela F., Annika Schwarz, Tibor M. Szikszay, Waclaw M. Adamczyk, Débora Bevilaqua-Grossi, and Kerstin Luedtke. "Physical therapy and migraine: musculoskeletal and balance dysfunctions and their relevance for clinical practice." Brazilian Journal of Physical Therapy 24, no. 4 (2020), 306-317. doi:10.1016/j.bjpt.2019.11.001.

This Masterclass / review article discusses current literature and clinical practice for physiotherapists working with patients with migraines.

 

Key Points
  • Migraines are under-diagnosed and under-treated.

  • Patients may present with episodic, highly frequent, or chronic migraines.
  • Neck pain is common as part of the migraine cycle, and is related to worse clinical presentations.

  • Most patients present with at least three of the following:
    • Increased prevalence of cervical trigger points.
    • Decreased cervical ROM.
    • Decreased cervical flexion and extension strength.
    • Decreased upper cervical rotation.
    • Forward head posture.
    • Decreased pressure-pain thresholds in the head and neck.

 

Convergence of the cervical and trigeminal nerves in the brainstem. Adapted from Haldemann and Dagenais, 2001.

  • A possible mechanism is the trigeminocervical complex: afferents from C1, C2, and C3 converge onto second-order neurons that also receive afferents from the first division of the trigeminal nerve.
  • "Accordingly, a dysfunction in the musculoskeletal area that has afferents into the trigeminocervical complex, may reinforce sensitization and thereby facilitate chronicity." (p. 308)
  • Nociceptive afferents from the TMJ may also sensitise this system.

 

  • Vestibular symptoms are inherent in the migraine condition, and can include the following symptoms:
    • Dizziness.
    • Vertigo.
    • Self-motion perception.
    • Spatial disorientation.
  • Postural control impairments such as decreased balance in quiet standing, and a reduction of the limits of stability are also observed.
  • Impairments in postural control deteriorate over time.
  • Balance deficits and vestibular dysfunction can be present in the absence of dizziness or other vestibular symptoms.
  • Sensory mismatch between the vestibular, visual, and proprioceptive systems can lead to a variety of vestibular symptoms.
  • Conflicting expected and perceived cues from labyrinthic, visual, proprioceptive, and exteroceptive afferents may be exacerbated by malfunction in the brainstem, cerebellum, inner ear, basal ganglia, and cortical hemispheres.
  • Delayed development of visual motion processing and orientation perception is observed in patients with migraine conditions.

 

Mobility and Exercise Recommendations for Treatment
  • Trigger point releases and stretching of the SCM and upper trapezius, combined with suboccipital treatment.
  • Combine with exercises to strengthen the neck and scapula control.
  • Thoracic and cervical mobility exercises are useful for those with decreased range of motion.
  • Cervical and thoracic strength training are also warranted, as there is evidence that these improve neck pain.
  • Nerve tissue mobilisation. (See our post on neurodynamics.)
  • Treat TMJ dysfunction if indicated.
  • High-intensity aerobic exercise.

 

Vestibular Recommendations for Treatment
  • Progressive gaze stabilisation exercises, visual motion desensitivity training, and vestibular habituation.
  • (Note: presence of migraines delays treatment success for vestibular rehabilitation.)
  • Balance and gait training, as well as global endurance and strength training are indicated for falls prevention.
  • Balance and gait training have not, however, been studied in a migraine population.

 

1. Haldeman S, Dagenais S. Cervicogenic headaches: a criticalreview. Spine J. 2001;1:31-46.

 

 

Shoulder Kinematics Impact Subacromial Proximities

Lawrence, Rebekah L., Jonathan P. Braman, and Paula M. Ludewig. "Shoulder kinematics impact subacromial proximities: a review of the literature." Brazilian Journal of Physical Therapy 24, no. 3 (2020), 219-230. doi:10.1016/j.bjpt.2019.07.009.

This literature review examines the relationship between shoulder kinematics and the aetiology of rotator cuff pathology.

 

Key Points
  • Subacromial compression is unlikely a contributing factor to rotator cuff pathologies.
  • There are limitations to 2D measurements when trying to quantify 3D relationships.
  • 3D techniques are not as broadly available.
  • There are extreme variations in metrics for quantifying the subacromial space.
    • The most common metric is the minimum distance; it quantifies the smallest distance between two structures.

  • A ‘‘painful arc’’ of motion between 700 and 1200 humerothoracic elevation is considered a hallmark sign of ‘‘impingement syndrome’’.
  • Cadaveric studies show that subacromial contact occurred most frequently between 300 and 900 humeral elevation; however, proximity areas were greatest between 600 and 1200 humeral elevation.
  • Beyond 900 humeral elevation, the subacromial space ‘‘no longer accommodated’’ the rotator cuff tendons, therefore it is important to consider tendon location when interpreting subacromial proximities.

  • In vivo studies generally report the acromiohumeral distance progressively decreases with increasing humeral elevation until a minimum occurs between approximately750 to 1200 of humerothoracic elevation before increasing again at higher angles.
  • The results of in vitro and in vivo studies suggest humeral elevation impacts subacromial distances.
    • The smallest proximities occur at a lower angle of humeral elevation.

  • The smallest distance between the rotator cuff tendon insertion and coracoacromial arch occurs between 400 and 750 of humerothoracic elevation.
  • On average, individuals with dyskinesis experience a higher reduction in acromiohumeral distance than individuals without dyskinesis (dyskinesis: 1.9 mm or 21%; without dyskinesis: 1.4 mm or 16%).

  • Scapular assistance tests may be used to investigate the effects of scapulothoracic kinematics on subacromial distances.
    • The test assesses the effect of altering scapulothoracic kinematics on patient symptoms by manually facilitating upward rotation, posterior tilt, and/or external rotation.
  • Scapulothoracic rotations form the basis of movement-based diagnostic classifications (e.g. insufficient scapular upward rotation).
  • The relationship between scapulothoracic upward rotation and subacromial proximities is not absolute but depends on the angle of humerothoracic elevation.
  • Subacromial proximities appear to be mostly affected by alterations in scapulothoracic upward rotation with or without concurrent alterations in posterior tilt.

  • The effect of scapulothoracic kinematics on subacromial proximities is dependent on the angle of humerothoracic elevation.
  • Changes in glenohumeral and scapular kinematics are associated with changes in subacromial proximities.

 

Clinically: Pilates in Practice
  • Scapular position relative to the thoracic cage, and relative to the humerus, matter: supine shoulder mobilisations at the Tower; dart vs diamond press vs baby swan will all change the ability of the thoracic cage to move underneath the scapulae. 
  • Mobility and stability at the sternoclavicular and acromioclavicular joint are relevant for impingement syndromes; hug-a-tree and ballet arms supine at various angles will facilitate mobility through different ranges. 
  • Balance around the upper, middle, and lower trapezius is key for integration with  serratus anterior: prone pulling straps on the Reformer; windmill and twist at the Tower. 
  • Assess glenohumeral joint rotation from a centred position to ensure teres major, lats, and pecs aren't driving: build strength of the long head of triceps and posterior detoid; rowing series.

 

 

 

 

Exploiting Biomechanics to Direct the Formation of Nervous Tissue

Pfister, Bryan J., Jonathan M. Grasman, and Joseph R. Loverde. "Exploiting biomechanics to direct the formation of nervous tissue." Current Opinion in Biomedical Engineering 14 (2020), 59-66. doi:10.1016/j.cobme.2020.05.009.

This review is a critical assessment of recent advances in the utilization of mechanical stimuli towards exploiting nervous tissue growth and formation. The authors discuss current in vitro systems designed to restate the mechanical environment of developing neural tissues, and the advancements made in integrating these systems into the clinical setting.

 

Key Points
  • Mechanics can be used to guide and accelerate neuronal expansion.

  • The central nervous system plays a key role in initiating the autonomic functions and coordinated actions of every being.
  • The peripheral nervous system coordinates signal transmission between the central nervous systems and the peripheral organs.
  • Neurons have a natural ability to detect mechanical changes in the environment and respond to mechanical loading.
  • Axon growth is characterized by navigation of axons through embryonic tissues to form connections at synapses or terminate at end organ receptors and neuromuscular junctions.
  • Axons continue to grow as the organism expands in size, by several orders of magnitude.

  • It is important that axons develop the ability to adapt to biomechanical forces.
    • An inability to adapt may cause the disconnection of axons from their synaptic targets, considering that tissues expand naturally or change shape during the course of development.
  • Mechanics are involved in the growth of the brain.
    • Studies have shown that during gestation, the cortex expands at a rate of 2.5x over 6 weeks. 
    • As the brain develops, it places tension on white matter axons thus limiting cortical growth.
  • Axon stretch growth and cortical growth have limiting differential rates which may play a role in cortical folding during development.

  • Tissue growth can be induced using mechanical stretch.
  • Gradual traction on living tissues creates stress that stimulates the regeneration and maintenance of active growth of certain tissues.
  • With sufficient blood supply, steady traction of the tissues activates biosynthetic and proliferative functions.1

  • Stretching of connective tissues causes nerve epineurium and constriction of the vasculature, with consequential temporary or long-term palsy.
  • Stretch-growing of nerves in culture can be achieved by gradual acceleration of the expansion rate, below the rate at which the axon can grow.
  • It is possible to avoid neurological complications and pain by gradual application of stretch during limb lengthening (1mm daily).

  • Growth cone advancement is driven by mechanotransduction and force generation of cytoskeletal dynamics.
  • Lengthening of axons can be induced by the application of force on the distal ends of the axons – a result of the stretch growth technique.
  • Axons can withstand a constant application of 25% strain while accommodating normal axon growth.
  • Constant application of strains above 25% may result in chromatolysis and disconnection.
  • Skin expansion shares similar mechanical parameters and limitations as nerve tissue response to stretch growth. Gradual expansion of tissue expanders increases growth and reduces viscoelastic retraction.2

  • There is a correlation between integrin expression within axons and their regenerative capacity.
  • Increases in axon tension leads to elongation and growth. Conversely, reduction in tension leads to retraction of the neuronal process.

 

Clinically: Pilates in Practice
  • Stretching is an important component of neural regeneration and rehabilitation.
  • Consider that what a constant stretch of 10-20% of range is, and stay within that range  to integrate neurodynamics and/or other functional mobility exercises. (See  Neurodynamics article.) Drawing the sword; footwork sprung below at the Tower; spine stretch series; inversion work. 
  • Daily traction is required, so encourage low-load stretching (always less than 25%) at regular intervals. 

 

1. Hosny GA. Limb lengthening history, evolution, complications and current concepts. J Orthop Traumatol. 2020;21(1):3. Published 2020 Mar 5. doi:10.1186/s10195-019-0541-3

2. Purnell CA, Gart MS, Buganza-Tepole A, Tomaszewski JP, Topczewska JM, Kuhl E, Gosain AK. Determining the Differential Effects of Stretch and Growth in Tissue-Expanded Skin: Combining Isogeometric Analysis and Continuum Mechanics in a Porcine Model. Dermatol Surg. 2018;44(1):48-52. Epub 2017/07/12. doi: 10.1097/DSS.0000000000001228. PubMed PMID: 28692604; PMCID: PMC6004345.

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