Combined Neurophysiologic and Neuroimaging Approach to Reveal the Structure-Function Paradox in Cervical Myelopathy

Abstract

Objective:To explore the so-called “structure-function paradox” in individuals with focal spinal lesions by means of tract-specific MRI coupled with multi-modal evoked potentials and quantitative sensory testing.Methods:Individuals with signs and symptoms attributable to cervical myelopathy (i.e., no evidence of competing neurological diagnosis) were recruited in the Balgrist University Hospital, Zurich, Switzerland between February 2018 and March 2019. We evaluated the relationship between the extent of structural damage within spinal nociceptive pathways (i.e., dorsal horn, spinothalamic tract, anterior commissure) assessed with atlas-based MRI , and 1) the functional integrity of spinal nociceptive pathways measured with contact heat-, cold-, and pinprick- evoked potentials and 2) clinical somatosensory phenotypes assessed with quantitative sensory testing.Results:Sixteen individuals (mean age 61 years) with either degenerative (N=13) or post-traumatic (N=3) cervical myelopathy participated in the study. Most individuals presented with mild myelopathy (modified Japanese Orthopaedic Association score (mJOA)>15; N=13). 71% of individuals presented with structural damage within spinal nociceptive pathways on MRI. Yet, 50% of these individuals presented with complete functional sparing (i.e., normal contact heat-, cold-, and pinprick- evoked potentials). The extent of structural damage within spinal nociceptive pathways was neither associated with functional integrity of thermal (heat: p=0.57; cold: p=0.49) and mechano-nociceptive pathways (p=0.83) nor with the clinical somatosensory phenotype (heat: p=0.16; cold: p=0.37; mechanical: p=0.73). The amount of structural damage to the spinothalamic tract did not correlate with spinothalamic conduction velocity (p>0.05; rho=-0.11).Conclusions:Our findings provide neurophysiological evidence to substantiate that structural damage in the spinal cord does not equate to functional somatosensory deficits. This study recognizes the pronounced structure-function paradox in cervical myelopathies and underlines the inevitable need for a multi-modal phenotyping approach to reveal the eloquence of lesions within somatosensory pathways.

Proposing a Framework to Understand the Role of Imaging in Degenerative Cervical Myelopathy: Enhancement of MRI Protocols Needed for Accurate Diagnosis and Evaluation

“…Martin et al 27 used microstructural MRI, in particular T2* gray matter/white matter ratio assessment, to identify subclinical evidence of spinal cord damage in a cohort of patients with cervical stenosis, thus confirming promise. This finding is supported by similar studies using multimodal evoked potentials, suggesting solutions may also lie outside of imaging 35,36. Whatever the modality, the development of assessments to unlock this conundrum is crucial: being able to identify who requires surgery, and perform it before there is irreversible damage, would transform outcomes for DCM, moving it from a paradigm of reactive to pre-emptive care 5…”

“…This finding is supported by similar studies using multimodal evoked potentials, suggesting solutions may also lie outside of imaging. 35 , 36 Whatever the modality, the development of assessments to unlock this conundrum is crucial: being able to identify who requires surgery, and perform it before there is irreversible damage, would transform outcomes for DCM, moving it from a paradigm of reactive to pre-emptive care. 5 …”

SCIseg: Automatic Segmentation of T2-weighted Intramedullary Lesions in Spinal Cord Injury

“…While the model generalizes reasonably well to DCM lesions, there is a scope for improvement, especially, by adding the DCM cohort to the existing training set or by training a DL model exclusively on DCM data. Previous studies have reported the presence of hyperintense T2-weighted lesions in up to 64% of DCM patients (13,39,40) and explored the relationship between structural and functional damages (41). Such studies would greatly benefit from an automatic DCM lesion segmentation method.…”

The Effect of Vocal Intonation Therapy on Vocal Dysfunction in Patients With Cervical Spinal Cord Injury: A Randomized Control Trial

“…Some studies conducted auditory perception assessment and analysis on patients with vocalization dysfunction after CSCI and concluded that their speech features were of a reduced volume, mostly short sentences, increased inhalation time ( Gadomski et al, 2021 ; OSCIS investigators et al, 2021 ), and deviations in articulation, articulation accuracy, and speech quality ( Tamplin et al, 2014 ; Scheuren et al, 2021 ). Although most CSCI patients can maintain the volume required for a normal conversation in a quiet room, patients may have difficulty raising the volume in the presence of other noises ( Berlowitz et al, 2016 ).…”

“…Vocal vocalization therapy (VIT) ( Thaut and Hoemberg, 2014 ) uses vocal music training to practice vocal function control problems caused by structural, neurological, physiological, psychological, or functional abnormalities of vocal organs ( Strohl et al, 2020 ). VIT directly stimulates the muscles associated with breathing, vocalization, articulation, and resonance and requires more sound control ( Scheuren et al, 2021 ) and intensity ( Rodrigues et al, 2021 ) than speech. Furthermore, VIT training can enhance respiratory muscle strength ( Tamplin et al, 2014 ; Zhang et al, 2021 ).…”