Alternative interpretation of needle electrode findings

George Kukurin — 2006-10-19T00:00:00Z

I read with interest the case report "Improvement of lower extremity electrodiagnostic findings following a trial of spinal manipulation and motion-based therapy" Chiropractic & Osteopathy 2006, 14:20

doi:10.1186/1746-1340-14-20.

Congratulations should go out to Dr. Morningstar for his contributions to the literature. However in perusing his Table 1, pre-post electrodiagnostic findings; it appears that there were very minimal, if any, changes reported in the needle portion of the EMG between pre and post interventions.

Before addressing specifically the data presented in table one, a very brief review of needle electrode examination (NEE) findings may be in order. Once the connection between the motor nerve and muscle is interrupted (denervation) the newly denervated muscle becomes irritable. 1 This irritability increases over time leading to spontaneous activity in the affected muscle. 1-2 The NEE can demonstrate the changes that occur in muscles following denervation. In healthy muscle, insertional activity stops soon after the needle is inserted into (or is further moved through) the muscle.1-2 In denervated muscle, as the muscle becomes more irritable, the appearance of insertional activity become prolonged or increases. Thus the earliest signs of muscle denervation may be increased or prolonged insertional activity. Furthermore, a healthy muscle at rest is electrically silent. With progressive post denervation irritability, the muscle fibers will spontaneously twitch. This spontaneous activity can be recorded as fibrillation potentials (Fib) on NEE examination. 2 Another category of spontaneous activity seen in denervated muscles is called the positive sharp wave (PSW). 3 On NEE, the difference between fibrillation potentials and positive sharp waves is based mainly on their appearance or morphology. 1-3

It should be noted that there is controversy regarding the mechanism for the generation of these two spontaneous potentials. In both, the underlying mechanism is denervation of the muscle. It has been postulated that PSWs represent action potentials generated from muscle fibers in an advanced state of atrophy. However it now appears that Fib and PSWs are the same recorded potentials. 3 There difference in appearance being explained by the physical relationships between the recording electrode and the spontaneously twitching muscle.3 In other words, an artifact generated from the technological complexities of the NEE itself. With this in mind let’s take a closer look at the data reported in table one.

According to Table one there were no changes in insertional activity, fibrillation potentials nor positive sharp wave activity pre/post intervention for the R Tibialis Anterior, R Tibialis Posterior, R Gluteus Medius, R Gastroc LAT nor the R Gastroc MED. For the right short head of the rectus femoris muscle, positive (increased) insertional activity was recorded pre-treatment. Post-treatment, this muscle exhibited spontaneous activity in the form of positive sharp wave forms. As noted above, it is important to remember that electromyography potentials seen on the needle electrode examination are dynamic. Increased insertional activity is often the only early needle electrode abnormality seen in cases of denervation. Over time, this increased insertional activity often progresses to fibrillation potentials. Later positive sharp waves develop either as the muscle atrophies over time or as simply an artifact which changes the appearance of fibrillation potentials and gives them a positive sharp wave form morphology.

Hence the NEE changes seen in the short head of the biceps femoris may simply represent the natural life cycle of denervation seen in that muscle over time.

The Peroneus Longus muscle, like most of the other muscles sampled, showed identical pre and post intervention NEE denervation activity.

This is no way discounts other positive clinical findings reported by Dr. Morningstar. Since the actual findings of other portions of the electrodiagnostic work-up were not reported, they may show objective changes/improvements in nerve conduction velocity. If this were the case, it would suggest improved re-myelination.

Unfortunately, the data as presented, suggests that the intervention described by Dr. Morningstar likely had little, if any, effect on muscle denervation as evidence by the NEE findings reported in table one. This should not be surprising because the clinical state of the patient often fails to correlate with electrodiagnostic changes. It would be interesting to see what, if any, pre versus post treatment changes occurred in nerve conduction studies, H-reflex and/or F-wave studies in table form.

Very Truly Yours,

George W. Kukurin DC DACAN

Board certified chiropractic neurology

Article Comments - 'Improvement of lower extremity electrodiagnostic findings following a trial of spinal manipulation and motion-based therapy'

Alternative interpretation of needle electrode findings