Chapter 29 Radiculopathy

Question 1

In a sensory radiculopathy of a single nerve root, would you expect sensory loss to be
A) severe in the discrete distribution of a dermatome or
B) vague and poorly localized paresthesias?

Answer 1

Because dermatomes overlap widely with adjacent dermatomes, it is very unusual for an isolated radiculopathy to present with severe or dense sensory disturbance. Paresthesias are usually poorly localizable.

Question 2

2. What PNS disorder is suggested by a discrete area of dense sensory loss? (459)

Answer 2

Well-defined dense numbness is more consistent with a peripheral nerve lesion than a radiculopathy.

Question 3

Which is more consistent with a radiculopathy of exactly one root: paralysis or weakness? (459)

Answer 3

Because muscles receive innervation from more than one nerve root, radiculopathy at just one level should result in weakness rather than paralysis.

Question 4

4. Which roots contribute to the brachial plexus but don’t have reliable associated muscle stretch reflexes? (459)

Answer 4

C5 and C6 contribute to biceps and brachioradialis. C7 is the chief supply to the triceps. C8 and T1 don’t have reliable associated muscle stretch reflexes, although abnormalities of C8 will sometimes suppress triceps.

Question 5

5. Which reflex is often unobtainable but when present and asymmetric could be a clue to an L5 radiculopathy? (459)

Answer 5

Although the quads allow testing of L3 and L4 and the ankle jerks allow testing of S1, there is no reliable muscle stretch reflex to test for L5. When present and asymmetric, the medial hamstring reflex can contribute to a clinical picture of an L5 radiculopathy.

Question 6

6. Can a patient have clinically significant radiculopathy with a normal spine MRI? (460)

Answer 6

Yes. Many causes of radiculopathy may not be apparent on MRI including vasculitides such as diabetes; infections including Zoster, HSV, CMV and Lyme disease; and infiltration with sarcoid or by tumor.

Question 7

7. Your patient describes pain in the neck, shoulder and anterior arm with paresthesias in the shoulder. You find abnormal spontaneous activity on needle study of deltoid, supraspinatus, infraspinatus, rhomboids, biceps and brachioradialis. Radiculopathy of which root is most consistent with this picture? (460)

Answer 7

This picture is most consistent with radiculopathy at C5. Paresthesias of C6, which also supplies these muscles, would include radial forearm, thumb and index finger.

Question 8

8. Horner’s syndrome is most associated with radiculopathy of which root? (460)

Answer 8

You would be most likely to find a Horner’s syndrome with a T1 radiculopathy.

Question 9

9. Which 3 muscle groups could be weak in an L3 or L4 radiculopathy? (460)

Answer 9

(460) Both L3 and L4 supply quadriceps and thigh adductors. Illiopsoas is more L3 than L4. To recap, L3 supplies quads, adductors and illiopsoas; L4 supplies quads and adductors.

Question 10

10. Name 3 muscles that move the ankle that are supplied by L5. (460)

Answer 10

L5 supplies tibialis anterior, tibialis posterior, and the peronei.

Question 11

11. An L5 radiculopathy could result in weakness of tibialis anterior, tibialis posterior and the peronei. Which ASIA exam key muscle is also supplied by L5? (460)

Answer 11

L5 supplies extensor hallucis longus.

Question 12

12. An L5 radiculopathy could result in weakness of tibialis anterior, tibialis posterior and the peronei. Extensor hallucis longus could also be affected. Name 2 hip muscles that L5 supplies.

Answer 12

(460) L5 supplies gluteus medius and tensor fascia latae.

Question 13

13. Three muscle sets are key muscles for an S1 radiculopathy, 1 each in the lower leg, thigh and hips. Name these three muscle groups. (460)

Answer 13

For an S1 radiculopathy, in the lower leg test the plantarflexors. In the thigh test the hamstrings. In the hips test the gluteus maximus. Plantarflexors, hammies, gluts.

Question 14

14. In an S1radiculopathy, the sensory disturbance is in the lateral foot, posterior calf and sole of the foot. Where’s the sensory disturbance in an L3 radiculopathy? (460).

Answer 14

In an L3 radiculopathy, the sensory disturbance is in the anterior thigh.

Question 15

15. In an L3 radiculopathy, the sensory disturbance is in the anterior thigh. Where’s the sensory disturbance in an L4 radiculopathy? (460).

Answer 15

In an L4 radiculopathy, the sensory disturbance is in the medial calf and medial foot.

Question 16

16. In an L4 radiculopathy, the sensory disturbance is in the medial calf and medial foot. Where’s the sensory disturbance in an L5 radiculopathy? (460).

Answer 16

In an L5 radiculopathy, the sensory disturbance is in the dorsum of the foot, the great toe and the lateral calf.

Question 17

17. In an L5 radiculopathy, the sensory disturbance is in the dorsum of the foot, the great toe and the lateral calf. Where’s the sensory disturbance in an S1 radiculopathy? (460)

Answer 17

In an S1 radiculopathy, the sensory disturbance is in the lateral foot, posterior calf and sole of the foot.

Question 18

18. In an L3 radiculopathy, the sensory disturbance is in the anterior thigh. Where is pain? (460)

Answer 18

In an L3 radiculopathy, pain is also in the anterior thigh and groin.

Question 19

19. In an L4 radiculopathy, the sensory disturbance is in the medial calf and medial foot. Where is the pain? (460)

Answer 19

In an L4 radiculopathy, pain is in the anterior thigh but not in the groin.

Question 20

20. In an L5 radiculopathy, the sensory disturbance is in the dorsum of the foot, the great toe and the lateral calf. Where is the pain? (460)

Answer 20

In an L5 radiculopathy, pain is in the posterolateral thigh and calf, extending into the great toe and dorsum of the foot. In other words, the pain is in the posterolateral thigh plus the distribution of sensory disturbance.

Question 21

21. In an S1radiculopathy, the sensory disturbance is in the lateral foot, posterior calf and sole of the foot. Where’s the pain? (460)

Answer 21

In an S1 radiculopathy, the pain is in the posterolateral thigh and calf, extending into the lateral toes and heel. In other words, the pain is roughly in the posterolateral thigh plus the distribution of sensory disturbance.

Question 22

22. Your patient with radiculopathy has pain that radiates into the foot. Which two root levels are the most likely cause? (460)

Answer 22

Pain radiating into the foot is more likely to be caused by L5 and S1 radiculopathies than L3 or L4.

Question 23

23. Your patient with radiculopathy has pain that radiates into the anterior thigh. Which two root levels are the most likely cause? (460)

Answer 23

Pain radiating into the anterior thigh is more likely to be caused by L3 and L4 radiculopathies.

Question 24

24. Can entrapment neuropathies such as carpal tunnel syndrome and cubital tunnel syndrome cause pain proximal to the entrapment?.

Answer 24

(461) Although entrapment neuropathies don’t result in proximal paresthesias, they can refer their pain proximally into arm and shoulder

Question 25

25. Both radiculopathies and entrapment neuropathies may result in proximal pain, thus making it difficult to distinguish them clinically. One way to tell them apart is with the distribution of paresthesia, but this may not be helpful in mild cases. Another way to tell them apart is the presence or absence of pain in which location?

Answer 25

(461) Suspect radiculopathy rather than entrapment neuropathy if a prominent pain complaint is in the back or neck and if pain is worse with movement of the back or neck.

Question 26

26. Do radiculopathies typically yield normal or abnormal nerve conduction studies?

Answer 26

(462) Radiculopathies usually result in nerve conduction studies that are normal. The value of performing nerve conduction studies in a case of suspected radiculopathy is in excluding conditions with abnormal studies such as entrapment neuropathy or plexopathy.

Question 27

27. Radiculopathy at which root may be confused clinically with an ulnar neuropathy?

Answer 27

(462) An ulnar neuropathy may appear clinically similar to a c8 radiculopathy.

Question 28

28. What is the most common peripheral nerve injury that can mimic an L5 radiculopathy?

Answer 28

(462) An L5 radiculopathy can present with leg pain, foot drop and paresthesias over the dorsum of the foot and lateral calf. These symptoms may also be caused by a peroneal neuropathy at the fibular head. Both result in leg pain, foot drop and paresthesias over the dorsum of the foot and lateral calf.

Question 29

29. Which nerve conduction study is uniquely suited for detecting an S1 radiculopathy?

Answer 29

(463) You would consider an S1 radiculopathy if you had asymmetric results for an H-reflex recorded at the soleus.

Question 30

30. Which nerve conduction studies can be helpful in detecting radiculopathy of L5 or S1?

Answer 30

(463) Both L5 and S1 radiculopathies may result in abnormal F-wave responses of peroneal and tibial nerves.

Question 31

31. If a radiculopathy results in axonal loss and weakness, what effect will this have on CMAPs in weak muscles?

Answer 31

(464) A radiculopathy resulting in axonal loss may cause diminished amplitude, slightly diminished conduction velocity and slightly prolonged distal latency. The latter two measures will not reach the respective 75% and 130% thresholds that require demyelination, as the effect distally is only from axon loss.

Question 32

32. Preston recommends routine nerve conduction studies in the work-up of an upper limb radiculopathy. In cases of suspected C6-7 radiculopathy, which additional nerve conduction study is recommended? (463)

Answer 32

In cases of suspected C6-7 radiculopathy, Preston suggests at least one internal comparison study of median vs ulnar or radial nerve to rule out a carpal tunnel syndrome.

Question 33

33. For both upper and lower limb radiculopathy work-ups, Preston suggests doing at least one SNAP. If you only get to do one SNAP, how should you choose which to do? (463)

Answer 33

Preston suggests doing at least one SNAP in the distribution of the suspected radiculopathy.

Question 34

34. Which is more important in the work-up of radiculopathy: motor or sensory nerve conduction studies?

Answer 34

(464) Nerve conduction studies can help differentiate radiculopathy from more distal problems such as plexopathy or peripheral nerve pathology because radiculopathies have normal SNAPs and the more distal pathologies have abnormal SNAPs. Sensory nerve conduction studies are the most important part of the nerve conduction assessment of suspected radiculopathy.

Question 35

35. What are three explanations a normal SNAP in an area of numbness? (465)

Answer 35

One explanation is that the lesion could be proximal to the dorsal root ganglion. This includes radiculopathies, spinal cord and central lesions. A second explanation is that the lesion is hyperacute, less than the sensory semana of six to ten days required for Wallerian degeneration. A third explanation is proximal demyelination with conduction block. To recap: 1) Proximal to dorsal root ganglion 2) hyperacute 3) proximal conduction block.

Question 36

36. In working up a suspected C7 radiculopathy, you find abnormal spontaneous activity and decreased recruitment of triceps and extensor carpi radialis, both of which have C7 innervation. For your next muscle to sample, justify your choice of selecting either flexor carpi radialis or extensor carpi ulnaris. (465)

Answer 36

You would chose flexor carpi radialis. The wrist flexors are median-innervated, whereas extensor carpi ulnaris would be a third radial muscle and thus not helpful in distinguishing a C7 radiculopathy from a radial neuropathy. The general principle of this question is that you must sample muscles of the same myotome but of different peripheral nerves.

Question 37

37. In working up a suspected L5 radiculopathy, you find abnormal spontaneous activity in extensor hallucis longus and medial gastrocs. For your next muscle to sample, justify your choice of selecting either gluteus medius or peroneus longus. (465)

Answer 37

You would chose gluteus medius because it is proximal. The general principle of this question is that you should sample proximal as well as distal muscles in a myotome to rule out peripheral polyneuropathy.

Question 38

38. In working up a C7 radiculopathy, which other myotomes would you sample and why? (466)

Answer 38

In working up a C7 or any other radiculopathy, you would sample the myotomes above and below to exclude a more widespread process.

Question 39

39. In what fraction of radiculopathies are paraspinal muscles abnormal? (466)

Answer 39

Paraspinals are abnormal in radiculopathy half of the time. Abnormal paraspinals clearly localize the lesion to the root or anterior horn. Normal paraspinals do not rule out radiculopathy.

Question 40

40. Paraspinals should always be examined in a radiculopathy work-up except for what subset of patients? (466)

Answer 40

Fibrillation potentials in paraspinal muscles may be a result of spinal surgery. It isn’t helpful to needle paraspinals after spinal surgery.

Question 41

41. Which radial muscle is most helpful to sample in a workup of a C8 radiculopathy? (466)

Answer 41

For a C8 radiculopathy, in addition to sampling APB and FDI, you would sample EIP.

Question 42

42. To work up a suspected L4 radiculopathy, name muscles from 3 peripheral nerves you could sample. (467)

Answer 42

To work up an L4 radiculopathy, you would start with the femoral knerve’s quads. You would also sample the deep peroneal nerve’s tibialis anterior and the adductor magnus which is supplied by both obturator nerve and tibial portion of sciatic nerve. Magnus means big – so big that it is supplied by two nerves. Quads; tibialis anterior; adductor magnus.

Question 43

43. Name 4 muscles you could sample for an L3 radiculopathy?

Answer 43

(467) For an L3 radiculopathy, you could test quads, illiopsoas, adductor longus and adductor magnus. Adductor longus has less L4 than does adductor magnus, so it might be a better muscle for an L3 work-up.

Question 44

44. To work up a suspected L5 radiculopathy, name muscles from 3 peripheral nerves above the knee you could sample.

Answer 44

To work up an L5 radiculopathy, above the knee muscles include, from proximal to distal, the gluteus medius from inferior gluteal nerve; the L5 paraspinals from dorsal rami; and the medial hamstrings from sciatic nerve. Just as the L4 dermatome is medial leg and L5 dermatome is lateral leg, the L5 medial hamstrings are more caudally innervated than the S1 lateral hamstrings.

Question 45

45. To work up a suspected L5 radiculopathy, name muscles from 3 peripheral nerves below the knee you could sample.

Answer 45

proximal to distal: from tibialis anterior from deep peroneal; tibialis posterior from tibial nerve; peroneus longus from superficial peroneal nerve. 2 Tibialis and peroneus have L5.

Question 46

46. To work up a suspected S1 radiculopathy, name 2 muscles from different peripheral nerves above the knee you could sample. (467)

Answer 46

To work up an S1 radiculopathy, above the knee muscles include, from proximal to distal, gluteus maximus from inferior gluteal nerve; and lateral hamstrings from sciatic or peroneal nerves.

Question 47

47. You are working up a suspected S2 radiculopathy. How many peripheral nerves supply S2 muscles below the knee?

Answer 47

(467) To work up an S2 radiculopathy, below the knee muscles are all supplied by the tibial nerve. These include plantarflexors and foot intrinsics.

Question 48

48. One day after acute injury to a nerve root, what are findings on needle study?

Answer 48

(466). One day after an acute root injury, the only findings on needle study are reduced recruitment in the affected myotome.

Question 49

49. How long does it take after acute root injury for abnormal spontaneous activity to develop in paraspinals (466)?

Answer 49

Paraspinals develop abnormal spontaneous activity 10-14 days after root injury.

Question 50

50. How long does it take after acute root injury for abnormal spontaneous activity to develop in hip muscles (466)?

Answer 50

Hip muscless develop abnormal spontaneous activity 2-3 weeks after root injury.

Question 51

51. How long does it take after acute root injury for abnormal spontaneous activity to develop in lower leg muscles (466)?

Answer 51

Lower leg muscless develop abnormal spontaneous activity 3-6 weeks after root injury.

Question 52

52. Name 3 changes in MUAP morphology that result from collateral sprouting. (467)

Answer 52

Collateral sprouting happens sooner in the proximal muscles. MUAPs become polyphasic with long durations and larger amplitudes.

Question 53

53. Which of these three changes in MUAP morphology happens first? (467)

Answer 53

The first change that collateral sprouting causes in MUAP morphology is polyphasicity.

Question 54

54. Months after collateral sprouting begins, which resolves first: abnormal spontaneous activity or decreased recruitment?

Answer 54

(467) Successful reinnervation resolves abnormal spontaneous activity before it resolves decreased recruitment.

Question 55

55. In patients with true radiculopathy, are false negative EMG studies qualitatively common or rare?

Answer 55

(467) In patients with true radiculopathy, equivocal or false negative studies are not uncommon.

Question 56

56. Preston points out that a limitation of EMG is that it is often difficult to localize a radiculopathy’s level. They cite a study that found that 2 root levels were most difficult to differentiate from one another. Which levels are these?

Answer 56

(468) It is most difficult to distinguish lesions of C6 from those of C7.

Question 57

57. Is it common or rare to find clinical weakness in a radiculopathy, and what impact does this have on the likelihood of finding decreased recruitment? (470)

Answer 57

In radiculopathies, significant weakness is rare, so decreased recruitment is also unusual. Were the study requested immediately after acute root injury, decreased recruitment would be the only possible abnormality, and it would be unlikely without significant weakness on exam.

Question 58

58. Is it possible for a purely demyelinating radiculopathy to result in EMG abnormalities? (470)

Answer 58

A purely demyelinating radiculopathy may rarely result in conduction block, weakness and decreased recruitment.

Question 59

59. Is it possible for a purely sensory radiculopathy to result in EMG abnormalities? (470)

Answer 59

A purely sensory radiculopathy is undetectable by EMG and nerve conduction studies.

Question 60

60. Is it common or uncommon for some muscles in radiculopathy’s myotome to be unaffected? (470)
61. If your patient has normal paraspinals but abnormal spontaneous activity in limb muscles, which NCS is most important in distinguishing radiculopathy from plexopathy? (470) As normal paraspinals are common in radiculopathy, the best NCS to distinguish between radiculopathy and plexopathy are the SNAPs in the distribution of the affected root. Normal SNAPs in a distribution of sensory complaints is consistent with a lesion proximal to the dorsal root ganglion. Normal SNAPs in the distribution of the affected root is more consistent with radiculopathy than plexopathy.

Answer 60

It is common for some muscles in a radiculopathy’s myotome to be spared.

Question 61

61. Is it common or uncommon for needle study of paraspinal muscles to be normal in a radiculopathy? (470)

Answer 61

It is common that a radiculopathy results in normal needle study of paraspinals. The book sites a study of 93 cases of radiculopathy in which roughly half of the paraspinals tested normal.

Question 62

62. What patient position is ideal for needle study of paraspinals? (470)

Answer 62

For optimal needle study of paraspinals, the patient should be side lying in a fetal position with the side to be studied facing up.

Question 63

63. EMG of a patient with radiculopathy shows polyphasic MUAPs in the paraspinals but fibs and positive sharps only in limb myotome muscles. What physiologic process could explain this? (470)

Answer 63

Paraspinal muscles are the first to be aaffected by radiculopathy and also the first to be reinnervated. This picture is consistent with a healing radiculopathy

Question 64

64. If your patient has normal paraspinals but abnormal spontaneous activity in limb muscles, which NCS is most important in distinguishing radiculopathy from plexopathy? (470)

Answer 64

As normal paraspinals are common in radiculopathy, the best NCS to distinguish between radiculopathy and plexopathy are the SNAPs in the distribution of the affected root. Normal SNAPs in a distribution of sensory complaints is consistent with a lesion proximal to the dorsal root ganglion. Normal SNAPs in the distribution of the affected root is more consistent with radiculopathy than plexopathy.

Question 65

65. Is it easy or difficult to know the exact root level of the paraspinal muscles that you needle during EMG? (470)

Answer 65

There is significant overlap in the innervation of the paraspinal muscles, especially the superficial ones. Abnormal spontaneous activity in paraspinals is very helpful in marking the lesion as at or proximal to the nerve root, but it is less helpful in determining the root level of the lesion. Limb muscles are more helpful for determining the root level.

Question 66

66. What components of EMG distinguish a radiculopathy or polyradiculopathy from motor neuron disease? (471)

Answer 66

A very important concept often overlooked by electromyographers is that EMG and NCS results can not distinguish between radiculopathy and motor neuron disease. (However in some polyradiculopathies F waves may be more abnormal than in motor neuron disease.)

Question 67

67. Although EMG is the same, motor neuron disease and polyradiculopathy are different clinically. Name one symptom that may be present in polyradiculopathy but absent in motor neuron disease.

Answer 67

471) Polyradiculopathy usually has prominent sensory symptoms of pain and paresthesias. Motor neuron disease is purely motor.

Question 68

68. Name one physical exam finding that could help distinguish ALS from polyradiculopathy. (471)

Answer 68

In polyradiculopathy you expect diminished muscle stretch reflexes in the affected myotomes. In ALS some muscle stretch reflexes may be diminished but some may be normal or increased.

Question 69

69. Why do we not perform needle study on paraspinals of patients who have had spinal surgery? (471)

Answer 69

After spinal surgery, fibrillation potentials may persist for years in the paraspinals. It’s not understood why.

Question 70

70. You find fibs in distal muscles only but suspect radiculopathy clinically. What physiologic process could explain this? What component of the study will help distinguish radiculopathy from a more distal lesion? (471)

Answer 70

You may find fibs in only distal muscles if proximal muscles have been reinnervated. You look for polyphasic, long duration MUAPs in proximal muscles and look for normal SNAPs in the sensory distribution of the affected root.

Question 71

71. What are the typical findings on EMG and NCS in lumbar stensosis? (471-2)

Answer 71

In lumbar stenosis, symptoms are usually intermittent and only occur when posture compresses the roots. Fixed EMG changes seldom occur.

Question 72

72. Preston lists four conditions other than radiculopathy that may result in fibrillations in the paraspinals. Name one such condition that is less likely to affect distal muscles. (472)

Answer 72

You can get fibs in proximal muscles, including paraspinals, from myopathies such as polymyositis that have with inflammatory or necrotic features.

Question 73

73. Name a condition that may cause fibs in paraspinals that may also result in brisk reflexes. (472)

Answer 73

Fibs in paraspinals may be caused by motor neuron disease such as ALS.

Question 74

74. Name a condition that may cause fibs in paraspinals that is the result of a poison. (472)

Answer 74

Fibs in paraspinals may be caused by botulism.

Question 75

75. Name a common condition that may cause fibs in paraspinals that may also cause abnormalities on NCS. (472)

Answer 75

Fibs in paraspinals may be caused by neuropathy of the dorsal rami as may be seen in diabetic polyneuropathy.

Question 76

76. What condition which is common in elderly patients may be difficult or impossible to distinguish from partial reinnervation of a bilateral L5-S1 radiculopathy? (472) .

Answer 76

Preston gives an example of a patient with slightly diminished amplitudes and conduction velocities in bilateral sural, peroneal and tibial nerve conduction studies. H reflexes are slightly prolonged and EMG shows denervation and reinnervation in distal leg muscles. This pattern is consistent both with partial reinnervation from a bilateral L5-S1 radiculopathy and with mild peripheral polyneuropathy. Preston says that a limitation of electrodiagnosis is the inability to distinguish these two pathologies

Question 77

77. Which one aspect of EMG and NCS is most helpful in distinguishing a C6-7 radiculopathy from median neuropathy? (473)

Answer 77

The one study that would best help distinguish between a C6-7 radiculopathy and a median neuropathy is the SNAP to the 2nd and 3rd digits. If the SNAP is abnormal, the lesion is distal to the root.

Question 78

78. If a patient has an intact ankle jerk, will an H-wave be present? (477)

Answer 78

An intact ankle jerk on exam means that H-wave should be present.

Question 79

79. If a patient has an absent ankle jerk, will an H-wave be absent? (477)

Answer 79

An absent ankle jerk does not mean that the H-wave will be absent; you may still get an H-wave despite an absent ankle jerk.

Question 80

80. Reinnervation is most often successful in which muscle? (478)

Answer 80

Preston says that not only are the paraspinals the first muscle to be reinnervated but they are also the most likely to be successfully reinnervated. Preston suggests this is one reason why paraspinals may be normal in roughly half of radiculopathies.