American Spinal Injury Association (ASIA) Impairment Scale

[Wise Young]

There is much confusion about the American Spinal Injury Association Classification of spinal cord injury, also called the ASIA Impairment Scale. Here is the definition again:

A = Complete: No motor or sensory function is preserved in the sacral segments S4-S5.

B = Incomplete: Sensory but not motor function is preserved below the neurological level and includes the sacral segments S4-S5.

C = Incomplete: Motor function is preserved below the neurological level, and more than half of key muscles below the neurological level have a muscle grade less than 3.

D = Incomplete: Motor function is preserved below the neurological level, and at least half of key muscles below the neurological level have a muscle grade of 3 or more.

E = Normal: motor and sensory function are normal.

Please note that the following is my interpretation of the ASIA Classification.

The definition is a little confusing because it is also a definition by omission. An ASIA A classification is the simplest. It simply means no motor *or* sensory in sacral S4-S5. If a person has rectal/anal sensation, that person is not an A. If the person has voluntary sphincter contraction, that person is not an A.

An ASIA B is relatively rare in that it is a person who has anal sensation but *no* motor function below the *neurological level*. This is a little tricky. The neurological level is not the *injury level*. The neurological level is the lowest segment that has normal motor and sensory function. So, for example, even if you had a C4 injury and started with a C4 neurological level and then recovered back C5 and C6, your neurological level is C6. Therefore, to be called an ASIA B, you must have some sensory function below C6. So, to be an ASIA B, you must have anal sensation. You don't need anything else but you must not have any motor function below the neurological level or else you would be an ASIA C.

A person is ASIA C if the person has at least sacral sensation and any motor function below the neurological level but less than half of the key muscles below the neurological level have a muscle grade of 3 or greater. By the way, if you have voluntary sphincter contraction, you are no longer ASIA B because the definition of ASIA B says no motor function preserved below the neurological level and voluntary sphincter contraction would represent motor function below the neurological level. If you are not an ASIA A and have any motor function below your neurological level, you would be at least ASIA C.

You would be an ASIA D if 50% or more of the key muscles below your neurological level have grades of 3 or more.

Wise.

http://carecure.rutgers.edu/spinewir...nalLevels.html

[This message was edited by Wise Young on 10-08-03 at 12:08 PM.]

[Jeff]

Having anal sensation and the ability to move my toes makes me an ASIA C. Wow. Never really put that together before. Hmmmm....the plot thickens.

~See you at the SCIWire-used-to-be-paralyzed Reunion ~

[NANDA]

Dr Young:
My brother is C5 injury level, he has anal and bladder sensation, his neurological level is now about C7 left, T2 right side, he has little motor function he is tartin pinch and grip in right hand and just pinch in his left hand, good trunk control, and he moves his right leg (hip, knee less than 3)and hip left side,
I thought he was ASIA B because his muscle grade was less than 3... this means he is an ASIA C?? Yes it is kind of tricky to get it.
Thanks

NANDA

[Wise Young]

Jeff, I should poll the rehabilitation centers around the country to see if they interpret the ASIA standard in the same way. One possibility is that some doctors may choose to call a person with both anal sensation and voluntary anal sphincter contraction an ASIA B if they have no voluntary somatic muscle contraction elsewhere. By the way, this situation should be relatively rare, probably less than 5% of the case. Most people who can voluntarily contract their anal sphincter should have other muscles that they can move. Wise.

[Wise Young]

Nanda, he sounds like a C to me. Wise.

[Jeremy]

Dr. Young would a person with an ASIA C type injury benift more from some of the recent or future treatments or would the type of AISA injury level not really matter?

[Kitten]

One thing that is not clear to me in the ASIA scale is the importance of anal/rectal sensation and/or control. Why is this so important? It seems that classifying injuries based on the amount of sensory/motor function below the injury site would be the most important factors.

[Wise Young]

jeremy & kitten,

The ASIA classification system is just so that clinician have a uniform standard of nomenclature. When clinician says that a person is "complete" or "incomplete", what does that mean? In 1990, those terms were not well defined. One clinician's "complete" was another's "incomplete", or vice versa. It was an intolerable situation, particularly because the term "complete" was being used to force a pessimistic diagnosis/prognosis on patients.

When we started to discuss the definition of "complete", it became clear how difficult it was to define spinal cord injury. For instance, suppose a person starts out with a C4/5 injury and starts out with a C4 (shoulder shrug) neurological level but recover C5 (biceps) and C6 (wrist extensors). Is this a "complete" or "incomplete" injury? Most clinicians would call this a "complete" injury but if the definition of no motor or sensory function below the level of injury was adopted, this would be an "incomplete" injury.

So after much debate, the ASIA committee decided that a "complete" spinal cord injury was any person who had a neurological level below which there was no neurological function. Since S4/5 is the lowest level on the spinal cord, this became the definition. Several studies have shown that this definition actually conforms fairly closely to most clinical diagnoses. All clinicians agreed that a person who has anal sensation or voluntary anal contraction is not "complete". The converse, however, is not true. There are some people who do not have anal sensation or sphincter contraction who may be considered "incomplete" by some clinicians. For example, a person with a low sacral injury may not have S4/5 function but still can walk. However, such cases are rare.

The ASIA classification system is based an an older classification system that was created by Hans Frankel at Stokes-Manneville in England. The Frankel classification system had the same lettering system. Frankel A meant "complete" spinal cord injury. Frankel B was sensory preservation with no motor function. Frankel C was sensory and motor preservation but the motor function was "not useful". Frankel D was sensory and "useful" motor preservation.

The Frankel classification was subjective in the sense that clinicians had to decide whether the motor function was useful. To make the classification more objective, the ASIA committee decided to adopt the criterion of 50% of the muscles showing a grade of 3 or greater. By the way, the muscle grading system came from the British also. A muscle grade of 1 indicates "flicker" movement, 2 indicates movement but not sufficient to support the limb against gravity, 3 indicates strength sufficient to oppose gravity, 4 indicates strength sufficient to move against opposition, and 5 is normal. So, a muscle grade of less than 3 indicates that the muscle is not strong enough to left the limb against gravity. If more than half of the key muscles cannot do that, the motor function is then considered not useful, i.e. ASIA C.

Although each segmental level controls multiple muscles, the ASIA committee decided to choose only 10 muscles to grade. These muscles each represent a particular segment. Note that there are some very big and important muscles that are not included. For example, the hamstrings (the ones at the back of the thigh) and the gluteus maximus (the one in the butt) both were not included in the key muscles.

In addition to the motor score, the ASIA standard requires testing of each sensory dermatome for pinprick and light touch sensation. Pinprick assesses pain sensation, carried by the spinothalamic tract. Light touch assesses proprioceptive (position) sense, carried by the dorsal column. Finally, the ASIA standard includes a questionaire called FIM which assesses the functional ability of the patient.

The classification system, the motor score, the sensory score, and the FIM score were never intended to be a full descriptor of the spinal cord injury. They are meant to be the minimal information that should be collected in all spinal cord injury patients. Several studies have suggested that the ASIA standard is predictive in about 80-85% of the patients. In other words, 15-20% of the patients may deviate substantially from the norm. Note also that the neurological examination is not as predictive when there is head injury involved, and as many as 25% of people who have spinal injury also have had some head injury.

Wise.

[Kitten]

Wise,

Thank you for this clarification. Now it makes much more sense to me.

[antiquity]

Pinprick assesses pain sensation, carried by the spinothalamic tract. Light touch assesses proprioceptive (position) sense, carried by the dorsal column.

Dr. Young, which pathway recognizes deep pressure sensation (a stiff poke) and what does it indicate in terms of axonal/neuronal preservation?

Thank you.

[Wise Young]

seneca, I am not sure. There is one paper in 1984 which describes the electrophysiological characteristics of cells that are backfired from the lateral reticular nucleus, and that these cells are responsive to deep pressure (noxious) stimulation of the limbs. Backfired means antidromic or backward activation by stimulating axons in the lateral reticular nucleus, a brainstem nucleus. So, there is a distinct possibility that the spinoreticular tract may carry such information.

Note that the spinoreticular tract is ascending counterpart of the reticulospinal tract. I was unable to find a picture of the former but the following is a picture of the reticulospinal tract

The spinoreticular tract which is the sensory tract that goes back to the brainstem is part of the anterior lateral tracts of the spinal cord, i.e. located in the front and side white matter column. The reticular formation neurons that receive the information then relays the signals to the parafascilar nucleus and intralaminar nuclei in the contralateral thalamus. It is believed to be selectively involved in the perception of deep pain.

• Menetrey D, de Pommery J and Besson JM (1984). Electrophysiological characteristics of lumbar spinal cord neurons backfired from lateral reticular nucleus in the rat. J Neurophysiol 52:595-611. Summary: Spinal neurons antidromically activated from either the lateral reticular nucleus (LRN) or immediately adjacent areas were identified in the rat lumbar spinal cord. In agreement with previous anatomical work (60), these neurons were widely distributed in both the dorsal and ventral horns of the spinal cord and could be subdivided into three main groups according to their location: a) deep ventromedial (DVM) cells, which project more substantially to the LRN than to other supraspinal targets; b) cells of the median portion of the neck of the dorsal horn (mNDH), which project exclusively to the LRN; c) cells lying in other parts of the dorsal horn (superficial layers, nucleus proprius, reticular extension of the neck), by their location, they are indistinguishable from cells projecting to other supraspinal targets. The probability is high that the DVM and mNDH cells contribute exclusively, or at least preferentially, to the lateral component of the spinoreticular tract (lSRT), defined as the direct spinal pathway to the LRN. Although electrophysiological properties of cells were clearly related to their spinal location, several subpopulations could be recognized in each of the three main groups. The majority of DVM neurons were in lamina VII, with some in laminae VI, VIII, and X. With the exception of a few lamina X cells, the DVM neurons had high conduction velocities. Four subpopulations of these neurons were recognized. a) Innocuous proprioceptive cells responded to small changes in joint position, some showing convergence of nonnoxious cutaneous inputs. b) High-threshold cells (approximately 50% of DVM cells). Seventy-five percent of these cells were excited from bilateral receptive fields (mostly symmetric) with noxious cutaneous pinching that extended to subcutaneous tissues. Their evoked responses had long-lasting postdischarges that continued up to several minutes after cessation of the stimulus. c) Inhibited cells had no demonstrable excitatory receptive fields and a high ongoing activity that was tonically depressed by pressure or pinch; poststimulus effects of long duration were observed. d) Cells with no resting discharge and demonstrable excitatory peripheral receptive fields. mNDH cells had recording sites at the medial border of the internal portion of the reticular area of the neck of the dorsal horn.(ABSTRACT TRUNCATED AT 400 WORDS).

[jb]

i'm an asia a but i can feel my hemorrhoids. why isn't that considered sensation of s4/s5? it's in the anal/rectal area.

[Wise Young]

jb,

Are you sure that you can feel your hemorrhoid? I assume that you are feeling pain in your rectum when you say that you are "feeling your hemorrhoid". I am not questioning the fact that you are feeling something in your rectum but it may not be sensation.

On the other hand, if you can feel a suppository being placed in your rectum, or pinprick around the edges of your anal sphincter, that is definitely feeling and I would say that you are not ASIA A but probably ASIA B or C, depending on whether you have any voluntary motor function below your neurological level.

Apparent sensation can come from a place in the body without being stimulated. In such a case, it may not be sensation, but neuropathic sensation or pain. It is sometimes called phantom feeling.

Wise.

[Wise Young]

seneca, I assumed that you would understand but did not state explicitly that we should be careful extrapolating finding concerning spinal tracts in rat to humans. While humans and rats have many similarities, they also differ in several important respects. First, the corticospinal tract in the rat is located in the dorsal column while it is located in the lateral column in humans. Second, animals have some prominent reflexes and are absent or suppressed in humans; they, for example, have a motor reflex called the cutaneous trunci reflex which contracts the skin that is stimulated, i.e. shaking a fly off when it lands on the skin. Third, most animals are of course quadripedal with tigher forelimb-hindlimb coordination than bipedal humans, as well as differences in locomotor reflexes.

Note that the differences are not as great as some people think. For many years, clinicians dismissed work being done in rats as being predictive of human motor recovery. I shared this belief and consequently did experiments on cats. However, after now nearly 15 years of observing how they walk, I am becoming more and more convinced that the mechanisms of sensation and walking are not that different in rats. The main problem, of course, is that there is a dearth of detailed neurophysiological data from human that tells us which spinal tract does what.

Wise.

[Redford]

Dr.Young,

You are so patient to take the time to answer questions.

I am very confused about where I am on the ASIA scale. I am a T-12/L-1 with no bowel/bladder control. I have never been tested by a doctor for sensory/motor function. I do walk with leg braces and crutches. Yesterday I did an hour on the treadmill.

Because I can walk am I considered incomplete or does the lack of B/B make me complete?