Disc Degeneration with Root Irritation: Disc Ruptures
“Thou cold sciatica, cripple our senators and make their limbs halt as lamely as their manners.”
—W. Shakespeare
Apatient with a mechanical compression of a lumbar nerve root will present with the complaint of leg (radicular) pain with or without associated pain in the back. However, it cannot be too strongly emphasized that the mere complaint of pain in the leg does not indicate, by itself, root irritation or root compression. Any painful lesion on the lumbosacral region may give rise to pain referred down the leg in a sciatic distribution. Diabetes can affect peripheral nerves and mimic sciatica due to a disc rupture (6,18).
Referred or “reflex” pain has the same neurophysiologic basis as the referred pain to the shoulder associated with gallbladder disease and the referred pain down the arm associated with myocardial infarcts.
Referred leg pain derived from mechanical insufficiency of the lumbar spine is rarely experienced below the knee: it is not associated with paresthesia, and there is no evidence of root tension, as reflected by limitation of straight leg raising (SLR) or the presence of a positive bowstring sign.
Disc Ruptures (Herniated Nucleus Pulposus)
To understand the clinical syndrome of lumbar root irritation and compression due to a disc rupture is to take the most important step in understanding all of low back pain. Although there is tremendous variation in the presentation of a patient with a disc rupture causing sciatica, there is a common thread of historical and physical features that allows for a fairly accurate clinical diagnosis.
Clinical Picture
History
Onset. It is fairly constant that a patient who has radicular pain due to a disc rupture has, or had, back pain in their history. The exception to this is the younger patient who may manifest only leg pain as a symptom of the disc rupture and at no time will have had back pain. However, most patients with a disc rupture will have experienced some degree of prodromal back pain for varying lengths of time (from minutes to years). It may be intermittent in its occurrence and extended over a considerable period of time, representing the instability phase that Kirkaldy-Willis et al. (31) has described. It may be acute, followed soon after by the onset of leg pain.
Approximately half of the patients will attribute their back pain to various forms of traumatic experience. This is especially prevalent in the litigation and compensation population but, in fact, is retrograde rationalization on the part of many patients. Experimental studies and careful statistical analysis of case histories (30) do not support the concept that direct trauma or sudden weight loading of the spine are the causal agents of disc rupture, although they may aggravate a preexisting asymptomatic degenerative condition.
Either in a gradual or sudden fashion, the pain will lateralize to the hip or leg. This moment of lateralization heralds the contact of the ruptured disc with the nerve root and may or may not be precipitated by a simple traumatic event, such as bending over in the shower to pick up the soap.
Location of pain. Various combinations of back, hip, and leg pain present. When trying to understand sciatica, think of five different areas: the back, the buttock, the thigh, the leg, and the foot. There may be symptoms in all five areas or only in a few of these areas.
The back. Back pain is considered to be pain localized to the midline lumbosacral region. Any radiation of pain from this area should most likely be considered lateralization of discomfort, and except for the vague referred pain, possibly indicative of radicular involvement. This is a rather controversial statement, but we think that as one gains more experience with radicular involvement, this historical feature will become more evident. Radiation to such areas as the sacroiliac joint region, the high iliac crest region, and the coccygeal region is more indicative of dural irritation than the commonly believed notion that the pain radiation represents muscular splinting of the back with referred pain. This is especially true if this referral is associated with leg pain characteristics as follows:
The buttock. In essence, the buttock is the proximal part of the leg (Fig. 11-1). The younger the patient, the more likely sciatica will be limited to the buttock and more proximal lower extremity. The nature of the pain in the buttock is usually one of a deep-seated, sometimes cramping pain that is especially aggravated by sitting.
 FIGURE 11-1 A: The proximal part of the leg is the buttock. Pain in the buttock is considered leg pain. B: Radicular pain will be confined to a nerve root distribution in the leg. |
The thigh. Pain in this area tends to be the sharpest component of sciatica and sometimes is described as having an associated superficial “burning-sensitive” feeling. For both L5 and S1 root involvement, it is located in the posterolateral or posterior thigh and not the lateral thigh. For higher lumbar root involvement, the sharp pain will be in the anterior thigh. Unless the patient has a very sensitive bowstring sign, pain is usually absent from the popliteal fossa.
The leg. The sensation in this area can be mixed. For L5 to S1 root compression, the prevailing discomfort is a cramp and almost viselike feeling in the belly of the gastrocsoleus or peroneal muscles. In addition, the patient may report a paresthetic discomfort in the lateral calf (fifth root) or back of the calf (first root). Most but not all adult patients with sciatica due to a herniated nucleus pulposus (HNP) will have pain below the knee. Again, the younger patient can be a trap, in that he
or she may have pain only in the high iliac crest region, the proximal buttock, and/or thigh. Although rare, this does occur, and offers much confusion in the assessment of the young patient with a disc rupture.
or she may have pain only in the high iliac crest region, the proximal buttock, and/or thigh. Although rare, this does occur, and offers much confusion in the assessment of the young patient with a disc rupture.
Higher lumbar root lesions (L2, L3, L4) will have no pain below the knee. In L4 root involvement, the patient will often describe a paresthetic discomfort down the medial shin (below the knee), but not pain.
The foot. Unlike the calf, the most common symptom in the foot is paresthesia rather than pain. The lateral border of undersurface of the foot is often, but not always, involved with 1st sacral root compression, whereas the dorsum of the foot may be affected with fifth lumbar root involvement. It is unusual that the patient will complain of pain in the foot.
The term sciatica implies that the patient has leg pain. The younger the patient with a disc rupture, the more likely the sciatic pain will dominate the history. It is a good general rule that, regardless of age, if the radiating hip and leg pain is, at all times, less significant to the patient than the complaint of back pain, the sciatica is not likely due to a disc rupture.
In general, pain derived from the L5 to S1 root involvement courses down the posterior aspect of the leg, whereas lesions of the second, third, and fourth lumbar roots give rise to pain on the anterior part of the thigh (39). It is routine for sciatic pain due to fifth and first root compression to radiate below the knee but, as often mentioned, the younger patient may not have this more distal radiation of discomfort. It is safe to teach that most sciatic pain due to root compression radiates below the knee, but there are exceptions to every generalization in medicine.
Paresthesia in the form of tingling, pins and needles, or numbness is of great value in localizing the level of root compression (29), and the more distal its location, the more reliable it is in helping with root localization. If a patient can volunteer that the paresthetic discomfort is along the lateral border of the foot into the little toe or up the back of the calf, one can assume that the most likely nerve root involved is S1. Similarly, paresthetic discomfort over the dorsum of the foot or lateral calf implicates the fifth lumbar nerve root; paresthesia over the medial shin indicates fourth lumbar root involvement. Similarly, paresthetic discomfort centered around the knee indicates third root involvement, and lateral thigh pins and needles indicates second root involvement. If the paresthetic discomfort or numbness is vaguely described and has a stocking-and-glove-like distribution, it is not indicative of radicular involvement and is more suggestive of a neuropathy or psychogenic pain. Rarely, motor symptoms predominate and are more disabling to the patient. In such instances, the clinician has to beware of the presence of a spinal tumor or a peripheral neuropathy. When trying to determine the localization of leg pain, have the patient put his/her foot up on a chair and then draw the location of their symptoms (Fig. 11-2).
Aggravation. Back and sciatic discomfort is spondylogenic in nature. That is to say, the pain is aggravated by general and specific activities and relieved by rest. Bending, stooping, lifting, coughing, sneezing, and straining at stool will intensify the pain. Which particular activity bothers a patient varies from patient to patient. Most patients with sciatica find difficulty in sitting, especially in a soft lounge chair, including most automobile seats. Standing and walking, although not comfortable, are usually more tolerable. Some patients may find other forms of activity aggravating, but a constant thread throughout the history of sciatica is the fact that some activity bothers the patient. The corollary is also true; if a patient with sciatica rests long enough, or gets into the proper position, some relief of the leg pain will ensue. Aggravation of sciatic discomfort by coughing and sneezing is one of the most commonly mentioned symptoms in textbooks. Although rather specific for radicular involvement, aggravation of pain due to coughing and sneezing is absent often enough from the history to be considered insensitive as a symptom.
Relief. Most patients get some relief from lying in the hip-knee flexed position (Fig. 11-2B). Sleeping is a more comfortable position for most patients when it is done with a pillow under the knees (Fig. 11-2C) or on the asymptomatic side in the fetal position. Some patients have so much sciatic discomfort that there is no position of comfort. This is especially true for the high lumbar root lesions.
Unusual referral patterns of pain. On occasion, unusual referral patterns of pain may occur, such as perineal or testicular discomfort and lower abdominal discomfort. Waddell and Main (55,56) have stated that referral of pain to the low sacrococcygeal region is suggestive of nonorganic involvement. We believe that just the opposite is true, in that patients with midline dural irritation will often refer discomfort to the lower sacrococcygeal region. Testicular pain is also common and somewhat
confusing. Obviously, anyone with testicular pain needs to evaluated for a local testicular cause of their discomfort. In some cases, this referral to the testicular region, or perineum in women, is again due to irritation of the midline sacral nerve roots. On a rare occasion, it is indicative of a higher lumbar disc lesion and represents the dermatomal radicular distribution of pain (L1 root).
confusing. Obviously, anyone with testicular pain needs to evaluated for a local testicular cause of their discomfort. In some cases, this referral to the testicular region, or perineum in women, is again due to irritation of the midline sacral nerve roots. On a rare occasion, it is indicative of a higher lumbar disc lesion and represents the dermatomal radicular distribution of pain (L1 root).
 FIGURE 11-2 A: Ask the patient to put the symptomatic foot up on a chair and draw the distribution of the leg pain. If he or she draws a line in a radicular distribution with one finger, you not only have the diagnosis of radicular syndrome—you can usually figure out which root is involved. B: Most patients with sciatica will have figured out that the fastest way to relief of some leg pain, when they get home from work, is to assume this position. C: The position of comfort when in bed (the semi-Fowler position). |
Severe sciatica. On occasion, you will encounter a patient who has so much leg pain that he or she will not be able to localize the symptoms. These are the patients who say either, “fix my leg pain or amputate my leg.” To persist in trying to get them to localize their leg pain or their paresthesias is fruitless. Get on with the examination and the diagnosis!
Physical Examination
The physical examination of a patient with sciatica due to a disc rupture is so variable as to be confusing. Some patients present with little in the way of back findings, with all of their findings confined to the lower extremities, whereas others present with incapacitating back spasm, sciatic scoliosis, and are significantly disabled. The common thread through this variable presentation is the fact that the majority of objective findings in a patient with sciatica due to a disc rupture will be in the lower extremity rather than the back.
The Back
The posture is characteristic. The lumbar spine is flattened and slightly flexed. The patient often leans away from the side of pain, and this sciatic scoliosis become more obvious on bending forward. The patient is more comfortable standing with the affected hip and knee slightly flexed, a manner accentuated by asking the patient to flex forward (Fig. 11-3). In the very acute phase, these patients will walk in obvious discomfort, sometimes holding their loins with the hands. The gait is slow and deliberate and is designed to avoid any unnecessary movement of the spine. With gross tension on the nerve root, the patient may not be able to put the heel to the floor and walks slowly and painfully on tip-toe. On rare occasion, this reaction may extend to needing crutches for ambulation.
 FIGURE 11-3 The classic posture in sciatica on forward flexion; the knee of the affected leg flexes while the hip rotates forward (external rotation of hip to relax pyriformis). |
Forward flexion may be permitted so the hands reach the knees by virtue of flexion of the hip joint. If the examiner keeps his/her fingertips on the spinous processes, it can be felt that the lumbar spine moves little because of splinting. Limitation of flexion in such instances is, therefore, the result of root tension and is due to the increase in leg pain. The degree of flexion should be recorded by measuring the distance between the fingertips and the floor.
Extension is also limited, although to a lesser degree than flexion, and in most instances the pelvis starts to rotate as soon as the patient attempts to lean backward. The complaint on extension is usually back pain, but at times the patient may feel leg pain. It is our impression that the complaint of leg pain on extension is indicative of an extruded or sequestered disc.
Lateral flexion can be full and free to one side, but usually lateral flexion toward the concavity of the sciatic curve (side of sciatica) is limited. The phenomenon of sciatic scoliosis and the relief of aggravation of pain on lateral flexion have been attributed to the position of the protrusion in relation to the nerve root (Fig. 11-4). However, this may be a simplistic explanation in view of the fact
that the sciatic scoliosis disappears on recumbency. This observation, the loss of lateral curvature of the lumbar spine on recumbency, differentiates the sciatic list from a fixed structural scoliosis.
that the sciatic scoliosis disappears on recumbency. This observation, the loss of lateral curvature of the lumbar spine on recumbency, differentiates the sciatic list from a fixed structural scoliosis.
 FIGURE 11-4 A: A disc herniation lateral to the nerve root. Theoretically, lateral flexion to the same side would increase the pain. B: An axillary disc herniation. Theoretically, lateral flexion to the opposite side increases the pain. |
Tenderness and Muscle Spasm
In the standing position, especially in the presence of scoliosis, muscle spasm can be observed. However, at rest, the spasm often subsides, and there is little tenderness to be found on examination. Selectively palpating and applying a lateral thrust to the spinous process may cause some back pain and, on the rare occasion, produce leg pain. The patient with sciatica due to a HNP, at complete rest in the prone position on the examining table, has little symptoms to be found in the back. The patient’s major complaint is leg pain, and the majority of physical findings are in the extremity.
The Extremities
The cardinal signs of lumbar root compromise are root tension, root irritation, and root compression.
Root tension and irritation. The term “root tension” denotes distortion of the emerging nerve root by an extradural lesion. The two most useful tests for the presence of root tension are limitation of SLR and the bowstring sign, the latter also arising in part from root irritation.
When testing SLR, it is important not to hurt the patient. Never jerk the leg up in the air suddenly. The knee must be kept fully extended by firm pressure exerted by the examiner’s hand, while the hip is slightly internally rotated and adducted. With the other hand under the heel, the examiner slowly raises the leg until leg pain is produced (Fig. 11-5). Two additional maneuvers are of vital importance to add significance to the finding of limitation of SLR:
Aggravation of pain by forced dorsiflexion of the ankle at the limit of SLR (a variation of Lasegue’s sign) (52,58)
Relief of pain by flexion of the knee and hip
Physiogenic sciatic pain due to nerve root tension is always relieved by flexion of the knee and hip. Further flexion of the patient’s hip with the knee bent does not reproduce and aggravate sciatic pain (Fig. 11-5). This phenomenon is only seen in the emotionally destroyed.
If SLR is permissible to 60 to 70 degrees before leg pain is produced, the finding is equivocal for an HNP. Below this level, the reproduction of pain on SLR, aggravated by dorsiflexion of the
ankle and relieved by flexion of the knee, is strongly suggestive of tension on the fifth lumbar or first sacral root. In patients in whom paresthesia in the foot is a predominant symptom, repetitive SLR, that is, “pumping of the leg,” frequently intensifies the sensation of numbness.
ankle and relieved by flexion of the knee, is strongly suggestive of tension on the fifth lumbar or first sacral root. In patients in whom paresthesia in the foot is a predominant symptom, repetitive SLR, that is, “pumping of the leg,” frequently intensifies the sensation of numbness.
 FIGURE 11-5 A: The standard for the straight leg raising (SLR) test: knee straight, hip neutral or slight internal rotation, and slow lifting of the leg by the heel. B: Hip and knee flexion should relieve the pain of radicular origin. |
Location of pain on SLR. The examiner is seeking to reproduce leg (buttock, thigh, and/or calf) pain when doing the SLR test. Reproduction of back pain, especially in the high ranges of SLR testing, is usually not indicative of root tension. However, there is one exception that is discussed later in this chapter under midline disc herniation.
False-positive SLR test. Hamstring tightness may cloud the assessment of the SLR test. Patients with hamstring tightness have a generally tight body build (e.g., inability to fully extend the elbow) and plenty of room between the wrist flexed, thumb abducted position, and the volar surface of the forearm (Fig. 11-6). Hamstring tightness should be bilateral, and the discomfort the patient experiences is distal in the thigh, in the region of the hamstring tendons. Hamstring tightness
does not radiate below the knee. Finally, other physical findings of root irritation and compression are absent in hamstring tightness.
does not radiate below the knee. Finally, other physical findings of root irritation and compression are absent in hamstring tightness.
 FIGURE 11-6 A: A tight-jointed individual with limited abduction of thumb. B: A loose-jointed individual with much greater passive abduction ability. |
False-negative SLR test. On occasion, you will encounter a loose-jointed individual with sciatica due to an HNP. On SLR testing, you may not be impressed with the degree of impaired SLR until you examine the unaffected leg and see the individual’s ability to straight leg raise well beyond 90 degrees.
Bowstring sign. The bowstring sign (7) is an important indication of root tension or irritation. The examiner carries out SLR to the point at which the patient experiences some discomfort in the distribution of the sciatic nerve. At this level, the knee is allowed to flex, and the patient’s foot is allowed to rest on the examiner’s shoulder (Fig. 11-7). The test demands sudden, firm pressure applied to the popliteal nerve in the popliteal fossa. The action may startle the patient enough to make him or her jump, and this jump may hurt. To prevent this, first of all, tell the patient that you are just going to press firmly on the back of the knee and that it may hurt. Apply firm pressure to the hamstrings; this will not hurt. Then, move your thumbs over to the popliteal nerve. A positive bowstring test is reproduction of radiating leg discomfort. Most commonly, the radiating discomfort is pain felt proximally in the thigh and even into the back. Less commonly, radiating discomfort will travel distally, and this discomfort is more often paresthetic in nature than painful. If the test produces only local pain in the popliteal fossa, it is of no significance. This demonstration of root irritation is probably the single most important sign in the diagnosis of tension and irritation of a nerve root caused by a ruptured intervertebral disc.
 FIGURE 11-7 The bowstring test. |
Tests to verify SLR reduction. When the patient sits with knees dangling over the side of the bed, the hip and knee are both flexed at 90 degrees. If the knee is now extended fully, the position assumed by the leg is equivalent to 90 degrees of SLR (Fig. 11-8). If the patient is suffering from root compromise, this will cause sudden, severe pain, and the patient will throw his or her trunk backward to avoid tension on the nerve. This is commonly referred to as the “positive flip test.” With the psychogenic regional pain syndrome, the patient will permit the examiner to extend the knee of the painful leg without showing any response at all.
 FIGURE 11-8 The flip test (staged). A: Negative. No backward flip on 90 degrees of straight leg raising (SLR) because there is no root tension. B: Positive. Physical root tension (SLR test) causes patient to flip posteriorly when straight leg is raised. |
Crossover pain (Well-Leg Raising Sign). There is some confusion as to what constitutes a positive crossed SLR test (61). Some have stated that a positive crossed SLR test occurs when you lift the symptomatic leg and produce pain in the asymptomatic leg. Historically, the original description of crossover pain was the reverse; that is, when lifting the well leg, pain crosses over into the symptomatic hip. Most people would agree that a positive crossed SLR test occurs when the well leg is lifted and the opposite symptomatic side becomes more painful. This is indicative of a disc herniation lying medial to the nerve root, either in the axilla of the nerve root or in a midline position.
A variation in the crossover pain test is the sitting SLR test. If in the sitting position, SLR of the well leg crosses pain over to the symptomatic hip, this is pathognomonic of an HNP. This test is valuable in assessing a patient with combined organic and nonorganic features. It is of value in assessing patients with acute back conditions who have significant back pain in the supine position on SLR tests. Some of them may be able to sit, and it is in this position that SLR testing can be done, with crossover pain being an early sign of an HNP, and the absence of SLR reduction or crossover pain indicating acute back muscle strain only.
Nonorganic Pain. If the patient complains of severe sciatic pain when attempting to bend forward, and there is a suspicion that there may be a significant degree of functional overlay, the patient should be asked to kneel on a chair. This will relax the hamstrings and reduce the tension of the sciatic nerve. In this position, the patient is asked to bend forward. With a physiogenic source of pain, the patient will be able to bend the spine and let his or her fingertips go below the level of the seat. In the nonorganic pain phenomenon, even with the knees flexed and the patient kneeling on a chair, he or she will not allow the spine to bend (Fig. 11-9).
Nerve root pain is probably the result of a combination of pressure and an inflammatory response to the prolapsed disc material. This “inflammatory response,” or “radiculitis,” has been loosely termed “root irritation.” Root irritation is an important factor in the demonstrated limitation of SLR, and it would appear to be productive of peripheral muscle tenderness. Such tenderness is not always present,
but, if demonstrable, it is of value in localizing the level of root involvement (15,51). Frequently, the calf is tender with S1 root lesions, the anterior tibial compartment is tender with L5 root involvement, and the quadriceps is tender when the fourth lumbar nerve root has been compromised.
but, if demonstrable, it is of value in localizing the level of root involvement (15,51). Frequently, the calf is tender with S1 root lesions, the anterior tibial compartment is tender with L5 root involvement, and the quadriceps is tender when the fourth lumbar nerve root has been compromised.
The shin is the body image of the leg, and very marked tenderness on palpating the subcutaneous surface of the tibia should warn the clinician that the patient has a large emotional content in this total disability. In the psychogenic regional pain syndromes, the patient frequently presents skin tenderness with pain on merely pinching the skin. Obviously, no meaningful statement can be made about the presence of deep muscle tenderness unless skin tenderness has been tested first. This is a trap for the unwary.
 FIGURE 11-9 Nonorganic reaction. The patient will not permit any flexion of spine despite relaxation of hamstrings. |
It should be noted that the upper quadrant of the buttock is a tender area in most people, with or without backache, and this area becomes increasingly tender in the presence of root irritation at any segment. The demonstration of this tenderness is of no localizing value. Patients with discogenic back pain with root irritation may also present tenderness over the sacroiliac joints and down the course of the sciatic nerve. This referred tenderness over the sacroiliac joint has given rise to confusion in the past, which results in the diagnosis of “sacroiliac strain” without any other clinical or radiologic evidence of damage to the sacroiliac joint.
Femoral nerve stretch. Figure 11-10 shows the femoral nerve stretch test. It is not nearly as satisfactory a test as is the SLR test but is considered positive when unilateral thigh pain is produced and aggravated by knee flexion (9), and it indicates tension on the second, third, or fourth lumbar roots. It is difficult to interpret in the presence of hip and/or knee pathology.
Impairment of root conduction (Root Compression). The diagnosis of disc rupture is in no way exclusively dependent on the demonstration of root impairment as reflected by signs of motor weakness, changes in sensory appreciation, or reflex activity. However, the presence of such changes reinforces the diagnosis (20,53). The common neurologic changes are documented in Table 11-1.
Changes in reflex activity. The ankle jerk may be diminished or absent with an S1 lesion. This is tested with the patient kneeling on a chair or sitting comfortably. If a patient’s sciatica is so bad that he or she cannot sit with comfort, do not test any reflex in the sitting position, as the subconscious guarding and posturing required of the patient to become less uncomfortable will upset the assessment of reflexes. This guarding and posturing explains the occasional depression of a knee reflex seen in the presence of sciatica due to an L5—S1 disc protrusion. If the patient has suffered from a previous attack of sciatic pain with significant compression of the first sacral nerve to obliterate the ankle jerk, this may not return to normal. The absence of an ankle jerk, therefore, may merely be a stigma of a previous episode of disc rupture, and the present attack may be due to a disc rupture at another level. Scratching the sole of the foot, as in the plantar
response, produces a reflex contraction of the tensor fascia femoris. This little-known reflex is often lost with an S1 lesion.
response, produces a reflex contraction of the tensor fascia femoris. This little-known reflex is often lost with an S1 lesion.
 FIGURE 11-10 The femoral nerve stretch test. |
With an L5 root compression, the tibialis posterior reflex (obtained by striking the tendon of the tibialis posterior near its point of insertion) may be absent. This is a pure L5 response. The clinician has to practice obtaining this reflex because it is not easy to elicit. Diminution of the lateral hamstring jerk is also seen on occasion with an L5 root compromise, but multiple innervation of this muscle group makes this an unreliable reflex. With L4 and L3 lesions, the knee jerk may be diminished.
Wasting. Muscle wasting is rarely seen unless the symptoms have been present for more than 3 weeks. Very marked wasting is more suggestive of an extradural tumor than a disc rupture.
The girths of the thigh and calf can be measured. This will act as a baseline, on occasion, to assess the progress of the lesion. It must be remembered that if there is gross weakness of the gastrocnemius, the main venous pump of the affected extremity is no longer working, and these patients may, indeed, show some measure of ankle edema. The combination of calf tenderness due to S1 root irritation and the observation of a swollen ankle may give rise to the erroneous diagnosis of a thrombophlebitis.
Table 11-1 Common Neurologic Changes in Herniated Nucleus Pulposus (HNP) | ||||||||||||||||||||||||||||||||||
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Motor Loss. The weakness of the gastrocnemii is best demonstrated by getting the patient to rise on tiptoe five or six times (Fig. 11-11). The patient is asked if it requires more effort to rise on tiptoe on the affected extremity. If the quadriceps are weak, the physician must be wary of this before ascribing the difficulty of tiptoe rising to weakness of the calf muscles. If sciatic pain is severe, the test cannot be performed by the patient. Jumping on tiptoe may be painful, and it is not a good method of examination, although slight weakness may be assessed by asking the patient to walk backward and forward across the length of the examining room on tiptoes to find out whether the gastrocnemii tire more easily.
 FIGURE 11-11 A: It is important to recognize the fact that when trying to assess the strength of the gastrocnemius by asking the patient to rise on tiptoe, this action must be carried out repetitively and rapidly. The examiner is really attempting to assess fatigability of the muscle. B: Ankle dorsiflexion (L4 and L5 roots) is best tested in this position of comfort. |
The power of ankle dorsiflexion is best tested by applying your full body weight to the dorsiflexed ankle (Fig. 11-11). Testing the dorsiflexor by asking the patient to walk on his/her heels will only demonstrate marked weakness in this muscle group. Weakness of the flexor hallucis longus (S1) or weakness of the extensor hallucis longus (L5) is often the first evidence of motor involvement. The evertors of the foot may be weak with an L5 lesion. The gluteus maximus may become weak with lesions involving the 1st sacral nerve root, and this weakness may be demonstrated by the sagging of one buttock crease when the patient stands (Fig. 11-12). Weakness of the gluteus medius is seen with an L5 lesion and occasionally is marked enough to produce a Trendelenburg’s lurch, particularly noticeable when the patient is tired. When the gluteus medius is involved, there is frequently marked tenderness on pressure over the muscle near its point of insertion, and this may be confused with a trochanteric bursitis or with gluteal tendinitis.
Quadriceps weakness is seen with an L4 and L3 lesion and can be assessed by the examiner placing his arm under the patient’s knee and asking the patient to extend the knee against the resistance of the examiner’s hand. However, this maneuver may produce pain, and a false impression of weakness is obtained. In such instances, it is better to have the patient lying face downward and flexing his or her knees to 90 degrees and then assessing the power to fully extend the knee from this position (Fig. 11-13).
 FIGURE 11-12 The gluteus maximus is supplied mostly by S1. Lesions involving the first sacral root may cause weakness of the gluteus maximus, which is apparent on examination by the sagging of one buttock crease. |
Sensory Impairment. The regions of sensory loss are reasonably constant (Fig. 11-14). Within each dermatome, there appear to be areas more vulnerable to sensory loss that others. Loss of appreciation of pinprick is first noted in an S1 lesion below and behind the lateral malleolus and in an L5 lesion in the cleft between the first and second toes. Sensory appreciation is a subjective
response and, as such, may at times be difficult to assess. Certain precautions must be followed. Sensibility varies in different parts of the limb. Identical areas in each limb must be tested consecutively. The examination must be carried out as expeditiously as compatible with accuracy, because the patient will soon tire of this form of examination, and answers may not be accurate. When the skin is pricked with a pin, the physiologic principle of recruitment is present. The overall sensory appreciation is dependent then not only on the action of the pinprick but also on the number of pinpricks experienced.
response and, as such, may at times be difficult to assess. Certain precautions must be followed. Sensibility varies in different parts of the limb. Identical areas in each limb must be tested consecutively. The examination must be carried out as expeditiously as compatible with accuracy, because the patient will soon tire of this form of examination, and answers may not be accurate. When the skin is pricked with a pin, the physiologic principle of recruitment is present. The overall sensory appreciation is dependent then not only on the action of the pinprick but also on the number of pinpricks experienced.
 FIGURE 11-13 Prone position for testing quadriceps strength. |
 FIGURE 11-14 The dermatomal areas supplied by each root where a sensory loss may be detected (left, L5; middle, L4; right, S1). |
A sensory examination is only interpreted as positive for a radicular lesion when the sensory loss approximates one dermatomal distribution, and the loss is not present in the adjacent ipsilateral dermatomes or the same contralateral dermatome.
AGE DIFFERENCE IN THE PRESENTATION OF A “DISC RUPTURE CAUSING THE ACUTE RADICULAR SYNDROME”
Throughout this discussion we have often referred to the different types of presentation for the acute radicular syndrome in young patients. In fact, the acute radicular syndrome from a disc rupture tends to have a characteristic presentation in the three age groups as outlined in Table 11-2.
Table 11-2 Clinical Picture of Sciatica in Different Age Groups | |||||||||
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