PMC5682302_01
First nerve conduction study (NCS) performed according to standard techniques on day 2 after admission. Right (A) and left (C) tibial motor NCS from abductor hallucis muscle following stimulation at medial ankle (upper trace) and popliteal fossa (lower trace), and corresponding right (B) and left (D) F-waves. Right peroneal motor NCS (E) from extensor digitorum brevis muscle following stimulation anterior to ankle (upper trace), below fibular head (middle trace), above fibular head (lower trace). Antidromic sensory NCS from left sural nerve (F) with recording from posterior ankle following stimulation at posterior-lateral calf, and from left radial nerve (G) with recording from snuffbox following stimulation over distal-mid radius. Right (H) and left (J) ulnar motor NCS from abductor digiti minimi muscle following stimulation at wrist (upper trace), below elbow (middle trace), above elbow (upper trace), and corresponding right (I) and left (K) F-waves. Right and left median and left peroneal nerves are not shown as their NCSs were also unremarkable. Note that motor and sensory responses of all testes nerves have normal latency, amplitude, and conduction velocity; tibial and ulnar nerve F-waves are normal bilaterally for latency, amplitude, configuration, and persistence; some A-waves are present bilaterally in the tibial nerve F-wave study.
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F1
All motor and sensory electroneurographies were normal, including F-waves (which were normal for minimal latency, persistence, amplitude, and morphology), except for the presence of A-waves in tibial nerves bilaterally (Figure 1, right and left median and left peroneal nerves not shown).
Second nerve conduction study according to standard techniques performed on day 25 after admission. No F-waves are recorded by supramaximal stimulation of right ulnar nerve at wrist; M waves are within normal range.
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F2
Five days later, repeat NCS revealed absent F-waves in right ulnar nerve (Figure 2), whereas F-waves in left ulnar and both tibial nerves still showed normal persistence and normal minimal latency; A-waves were still present in tibial nerves; there was no alteration of amplitude, morphology or duration of compound muscle action potentials (CMAPs) or sensory nerve action potentials (SNAPs); motor and sensory conduction velocities were all within the normal range; no conduction blocks were detected.
Third nerve conduction study performed according to standard techniques on day 50 after admission. Same nerves, stimulation, and recording conditions as in Figures 1A-K (A-K). Note marked amplitude reduction without temporal dispersion of both compound muscle action potentials and sensory nerve action potentials in all tested nerves with almost normal conduction velocities. Tibial nerve F-waves remain present and normal bilaterally, with some A-waves still present. Right ulnar nerve F-waves are now absent, with some A-waves present; left ulnar F-waves show reduced amplitude.
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F3
A repeat electrodiagnostic examination on day 50 revealed only slightly reduced conduction velocities, but then for the first time marked amplitude reduction without temporal dispersion of both CMAPs and SNAPs in all tested nerves; tibial nerve F-waves were still present bilaterally, with normal persistence, morphology and minimal latency; right ulnar nerve F-waves were still absent, and some A-waves were detected, left ulnar F-waves showed reduced amplitude (Figure 3).