Ch 17: Median Neuropathy Of The Wrist

Front 1

Radiculopathy of which 2 nerve roots is most likely to be mistaken clinically for CTS?

Back 1

(255) C6-7

Front 2

Your patient has a strong clinical picture for CTS, normal EMG, normal routine median and ulnar NCS but positive comparison tests between nerves. Is it common or rare for patients to present like this, with strong clinical picture for CTS but abnormalities only on the most sensitive comparison NCS tests?

Back 2

(255) Common

Front 3

3. Is it common or rare for patients to have little or no clinical findings of CTS and have definite findings of median neuropathy on NCS/EMG?

Back 3

(255) Common

Front 4

Name 3 thumb muscles supplied by the median nerve after it passes through the carpal tunnel.

Back 4

(257) APB, OP, superficial head of FPB

Front 5

Is CTS usually unilateral or bilateral?

Back 5

(257) Bilateral

Front 6

Is median mononeuropathy on NCS/EMG usually unilateral or bilateral?

Back 6

(257) Bilateral

Front 7

Does CTS usually effect both hands equally?

Back 7

(257,259 ) No. Dominant hand is usually more affected. If nondominant hand is more affected, look for identifiable specific cause such as mass lesion.

Front 8

How proximal may CTS pain may radiate?

Back 8

(257) CTS pain may involve hand, wrist, forearm, arm and rarely shoulder. The neck is not affected.

Front 9

If asked directly, most patients with CTS will admit that which digit is spared paresthesias?

Back 9

(257) Little finger

Front 10

In CTS, are nocturnal paresthesias common or rare?

Back 10

(257) Common

Front 11

In CTS, are sensory or motor fibers affected first?

Back 11

(257) Sensory

Front 12

In CTS, is functional impairment from reduced strength common or rare?

Back 12

(257) Rare

Front 13

Will most CTS patients have positive Tinel’s at the wrist?

Back 13

(257)Yes

Front 14

Is Tinel’s at the wrist qualitatively specific for CTS?

Back 14

No

Front 15

Which test, Phalen’s or Tinel’s, is better for CTS?

Back 15

(258) Phalen’s is more sensitive and specific.

Front 16

How long might you have to wait to get a positive Phalen’s in CTS? (258)

Back 16

2 minutes

Front 17

Why should Phalen’s be done with straight elbows?

Back 17

To avoid compressing the ulnar nerve at the cubital tunnel.

Front 18

19. Your patient has unmistakable NCS/EMG findings of median neuropathy but has no symptoms. Do they have CTS? Do they need treatment?

Back 18

(258-9) No and no.

Front 19

20. Your patient has paresthesias in the hand but no pain. Do these symptoms prejudice you in favor of or against a diagnosis of CTS?

Back 19

(258 Table 17-2); (261). Paresthesias and no pain are inconsistent with CTS (258 Table 17-2); always question the diagnosis of CTS in the absence of pain (261).

Front 20

Name 2 endocrine disorders associated with CTS.

Back 20

(259) DM, hypothyroidism

Front 21

Name 2 conditions which are more common in women which are associated with CTS.

Back 21

(259) Pregnancy, RA.

Front 22

Name a disease which is associated with CTS which could be thought to result in build up of proteins in the carpal tunnel.

Back 22

(259) Amyloidosis

Front 23

Suspect radiculopathy instead of CTS if there is pain in which location?

Back 23

(259) Neck

Front 24

25. Suspect radiculopathy instead of CTS if symptoms are made worse by motion around which body part?

Back 24

(259) Neck

Front 25

26. Pain from CTS may radiate into the forearm, upper arm and even shoulder. Can CTS paresthesias radiate in this distribution?

Back 25

(259) No; sensory abnormality in thenar eminence or proximally suggests alternative causes.

Front 26

If NCS show low median motor amplitudes, name 3 common classes of causes other than CTS.

Back 26

(261) Cervical radiculopathy, polyneuropathy, median neuropathy at elbow.

Front 27

What is more common in CTS: demyelination or axonal loss?

Back 27

(261-2) Demyelination.

Front 28

29. Your patient with clinical evidence of CTS has normal values for all median motor and sensory studies of the affected limb. What type of NCS that doesn’t involve the contralateral limb should be done next?

Back 28

(262) Comparison studies to ulnar and radial nerves.

Front 29

30. Even with optimal technique, is NCS a qualitatively sensitive means of detecting median neuropathy at the wrist?

Back 29

(262, 267) Yes. With inclusion of comparison studies to ulnar and radial nerves, ‘diagnostic yield’ is 95%. Page 267: 97% sensitivity.

Front 30

There are many comparison tests between median and ulnar or radial nerves. Typically the difference in distal latencies is considered significant if it is greater than what value?

Back 30

(262) 0.4ms to 0.5ms are cut-offs for the more common tests.

Front 31

32. If you overstimulate and cause depolarization of an adjacent nerve, can you reliably tell this from the shape of the wave form?

Back 31

(262) Not always; wave form may appear normal but you may nonetheless be getting bad data.

Front 32

Where do you stimulate in the palm for the median nerve palmar mixed nerve study?

Back 32

(264) Eight centimeters from the recording electrodes on a line connecting the median nerve at the wrist to the webspace between the index and middle fingers.

Front 33

Where do you stimulate in the palm for the ulnar nerve palmar mixed nerve study?

Back 33

(264) Eight centimeters from the recording electrodes on a line connecting the ulnar nerve at the wrist to the webspace between the fourth and fifth digits.

Front 34

35. Name an ulnar-median nerve comparative study that would be useful in assessing for CTS a patient who had diabetic polyneuropathy with an absence of both ulnar and median SNAPs in the hand.

Back 34

. (265) Median Second Lumbrical-vs-Ulnar Interossei distal motor latency comparison measures CMAPs so may be possible in such a patient.

Front 35

36. Where is the recording electrode (G1) placed for the Median Second Lumbrical-vs-Ulnar Interossei distal motor latency comparison test?

Back 35

(265) Just lateral to the midpoint of the third metacarpal.

Front 36

37. The amplitude of the APB CMAP when stimulating at the palm divided by the amplitude when stimulating just proximal to the wrist should not be greater than what number in normals?

Back 36

(267) Amplitude ratio greater than 1.2 is abnormal and suggests conduction block with demyelination.

Front 37

38. Name 2 possible sources of error that could change the amplitude ratio for the aforementioned comparison.

Back 37

(267) Stimulations might not be supramaximal (many causes including poor stimulus site and inadequate stimulus), and an adjacent nerve may be inadvertently activated

Front 38

39. If the amplitude of the APB CMAP when stimulating at the palm divided by the amplitude when stimulating just proximal to the wrist is 3, would this be better explained by a purely focal demyelinating or a purely axonal loss lesion?

Back 38

(267) This would be consistent with conduction block from a focal demyelination.

Front 39

40. What is the technical difficulty which makes difficult the radial vs median thumb SNAP comparison?

Back 39

(268) The median nerve travels to the thumb at an angle, making it difficult to measure the true distance.

Front 40

41. In normal people, is conduction velocity of median SNAP faster in the wrist to palm segment or the palm to finger segment?

Back 40

(269) In normals, the wrist to palm segment is faster because the nerve fibers are larger and warmer proximally.

Front 41

42. What differential of median sensory conduction velocity between palm to finger and wrist to palm segments is consistent with CTS?

Back 41

(269) If the palm to finger segment is > 10m/s faster than the wrist to palm segment, this is consistent with CTS.

Front 42

Which is the key muscle to EMG to assess for CTS?

Back 42

(271) APB

Front 43

Your needle study of APB is normal. Does this rule out CTS?

Back 43

(271) no

Front 44

Radiculopathy of which 2 dermatomes is most likely to mimic the paresthesias of CTS?

Back 44

(271) C6, C7

Front 45

Name 2 muscles supplied by the median nerve and innervated by C6-7

Back 45

(271) pronator teres, flexor carpi radialis

Front 46

47. Your exhaustive NCS to r/o CTS is normal. EMG of APB, PT and triceps is normal. H&P doesn’t suggest other neurogenic causes of symptoms. According to the algorithm on p271, how many further muscles need you test to complete your study?

Back 46

(271) none.

Front 47

If you highly suspect entrapment of the median nerve at the PT, what findings would you expect to find with needle study of the PT?

Back 47

(273) The PT is spared in entrapment of the median nerve at the PT. In general, the muscles for which the entrapment syndromes are named (piriformis, supinator, PT) are spared in entrapment syndromes, as innervation occurs proximal to the nerve piercing the muscle.

Front 48

Distal latency greater than what percentage of upper limit of normal is evidence of demyelination?

Back 48

(274) If distal latency is greater than 130% of the upper limit of normal, axonal loss with drop out of the fastest fibers is not sufficient to explain this slowing; demyelination must be part of the pathology.

Front 49

Conduction velocity less than what percentage of the lower limit of normal is evidence of demyelination?

Back 49

(274) If the conduction velocity is less than 75% of the lower limit of normal, axonal loss with drop out of the fastest fibers is not sufficient to explain this slowing; demyelination must be part of the pathology.

Front 50

51. Is it common or rare for patients with severe CTS to have diminished conduction velocity in the forearm?

Back 50

(274) It is common for patients with severe CTS to have diminished conduction velocity in the forearm. This may be due to axonal loss and drop out of the fastest fibers or from conduction block at the wrist affecting the fastest fibers most. It does not imply additional lesions.

Front 51

52. Name a non-endocrine disease which predisposes you to CTS, radiculopathy, distal symmetric sensorimotor polyneuropathy, and vasculitic neuropathy resulting in mononeuritis multiplex.

Back 51

(277) Rheumatoid arthritis.

Front 52

Is it common or rare for a patient to have clinical CTS with all NCS and EMG tests normal?

Back 52

(278) This is rare. In these patients there is no demyelination or axonal loss, but transient ischemia from intermittent compression.

Front 53

54. The role of EMG/NCS in CTS includes confirming diagnosis and looking for possible coexisting conditions. How does the study help determine treatment?

Back 53

(274, 278) EMG/NCS helps determine treatment by assessing severity. Case 1 showed a patient with chronic axonal loss and reinervation; this patient would need surgical referral.