Neurological measurements: Introduction
Introduction 31
3.2.1 Motor
1 Medical Research Council grading system 44
2 Hand-held dynamometer 45
3 Wolf motor function test (WMF) 46
4 Jebsen-Taylor hand function test (JTHF) 47
5 9-hole peg test 48
6 Graded and redefined assessment of strength, sensibility and prehension (GRASSP) 49
3.2.2 Sensory
1 American Spinal Injury Association (ASIA) impairment scale—sensory 50
2 Quantitative sensory testing (QST) 51
3.2.3 Tone and reflexes
1 National Institute of Neurological Disorders and Stroke (NINDS) myotactic reflex scale 52
2 Ashworth scale 53
3.2.4 Autonomic
1 ASIA impairment scale—autonomic 54
3.2.5 Walking
1 10-meter walk test (10MWT) 55
2 30-meter walk test (30MWT) 56
3 50-foot walk test (50FWT) 57
4 Timed up and go test (TUG) 58
5 10-second step test (10SST) 59
6 Walking index for spinal injury (WISC-II) 60
7 Spinal cord injury functional ambulation inventory (SCI-FAI) 61
3.2.6 Composite scales
1 ASIA / International Medical Society of Paraplegia (IMSOP) 62
2 Functional independence measure (FIM) 63
3 Spinal cord independence measure (SCIM) 64
4 Rivermead mobility index (RMI) 65
5 Barthel index 66
6 Fugl-Meyer assessment 67
Introduction
Spinal examination allows for localization of spinal cord pathology along the rostrocaudal axis and the transverse plane. It creates an objective correlation between clinical deficits and radiographic findings, thereby helping to predict the necessity and benefit of surgical intervention. A careful observation of the patterns of deficits will also allow for discrimination between true spinal pathology and nonneurological disease. In this chapter we will discuss measurements of function on the spinal examination. We will explore current clinical scores and scales of spinal disease, focusing specifically on quantifiable tests of motor and sensory performance, reflexes and complex function. An overview of these tests can be found in Table 3.2-1 .
Motor
The Medical Research Council grading system
The most widely used measurement of motor strength is the Medical Research Council (MRC) muscle strength grading system. The MRC grading system is a 5-point ordinal scale ranging from 0 (no visible muscle contraction) to 5 (full strength). Its origins date back to World War II, when the Nerve Injuries Committee of the British Army published Aids to the Investigation of Peripheral Nerve Injuries [1] in the hope of creating a quantifiable grading scale to measure recovery in patients with traumatic nerve injuries resulting in paralysis. Since its first publication in 1943, the MRC grading system has attracted considerable debate. While it is supported by reasonable interobserver and intraobserver reliability [2], it is heavily reliant on a limb′s ability to perform against gravity and the percentage of total strength required to raise a limb against gravity, which varies between muscle groups [3]. In electro-physiological studies, the brachii muscle requires ~2% of total strength to raise the forearm against gravity, hip abductor muscles require 24%, and supinator muscles require < 1% [4]. Similarly, cadaveric studies have shown that total torque required to flex the elbow against gravity is as low as 4% [5]. Therefore the single grade 4/5 represented more than 96% of total functional ability. Bearing in mind that the original intention of the MRC grading system was to track subtle improvements in patients with post-traumatic paralysis, it is reasonable that the scale is heavily biased towards small, objective improvements in motor function (grades 0–3) with disproportionally large jumps between high strength grades (grades 4–5). However, when used in the context of degenerative disc disease where patients typically retain near-full strength, the 5-point grading system becomes less objective and more reliant on the subjective proprioception of the examiner. While many other functional manual motor tests (MMTs) exist and will be addressed later, the MRC grading system remains the dominant scale in assessing motor function for its simplicity. It has also been incorporated into many of the composite grading systems. The American Spinal Injury Association (ASIA)/International Medical Society of Paraplegia (IMSOP) impairment scale is a multifaceted classification system of spinal cord injury that has been adopted by many physicians who manage acute spinal cord injury. The motor arm of the scale incorporates the MRC grading system for testing muscle strength. The algorithm used to calculate the ASIA score can be found in Fig 3.2-1a–b . In combination with sensory examination, the level and lateralization of the MRC grade is used to determine the single neurological level (the lowest segment where motor and sensory function is normal, on both sides, and the most cranial of the sensory and motor levels). The ASIA/IMSOP impairment scale will be discussed in greater detail later.
Quantified muscle tests
Efforts have been made to create quantified muscle tests (QMTs) to allow for concrete measurements of muscle function, particularly in clinical research. QMTs use dynamometric equipment to get an absolute measurement, in kilograms or newtons, of a muscle groups’ strength. Unfortunately, they often require bulky equipment and are heavily reliant on the technician′s skill. They have been criticized for a lack of standardized clinical relevance. While a value given in MMT scales reflect the functional ability of a patient (ie, for a limb to overcome gravity), the value at which a dynamometric measurement implies clinical change is poorly defined (ie, at what value can a patient feed themselves). Nonetheless, the hand-held dynamometer is a portable and objective tool that shows promise of becoming a simple and concrete method of following rehabilitation or disease progression.
Upper extremity testing
The motor performance of the hand has unique implications in quality of life. The Wolf motor function test (WMF), the Jebson-Taylor hand function test (JTHF), and the 9-hole peg test are tests specifically focused on the complex function of the upper extremity. The WMF and JTHF both test commonly performed manual tasks (ie, writing, reading, feeding, and manipulating objects). While the JTHF is scored based on time required to complete each task, the WMF has both timed and force-based components that are further scored on quality of movement. The 9-hole peg test is a timed examination wherein the patient places and then removes dowels from nine set holes. While the WMF and JTHF are appropriately detailed for a research setting, the nine-hole peg test provides a convenient and easily reproducible test of fine motor skill that may be more applicable to the clinical setting. The graded and redefined assessment of strength, sensibility and prehension (GRASSP) is a battery of tests quantifying upper extremity function [6].
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