Comparison of electric and magnetic coil stimulation in the supraclavicular region

Piezoelectric Signals in Vascularized Bone Regeneration

The demand for bone substitutes is increasing in Western countries. Bone graft substitutes aim to provide reconstructive surgeons with off-the-shelf alternatives to the natural bone taken from humans or animal species. Under the tissue engineering paradigm, biomaterial scaffolds can be designed by incorporating bone stem cells to decrease the disadvantages of traditional tissue grafts. However, the effective clinical application of tissue-engineered bone is limited by insufficient neovascularization. As bone is a highly vascularized tissue, new strategies to promote both osteogenesis and vasculogenesis within the scaffolds need to be considered for a successful regeneration. It has been demonstrated that bone and blood vases are piezoelectric, namely, electric signals are locally produced upon mechanical stimulation of these tissues. The specific effects of electric charge generation on different cells are not fully understood, but a substantial amount of evidence has suggested their functional and physiological roles. This review summarizes the special contribution of piezoelectricity as a stimulatory signal for bone and vascular tissue regeneration, including osteogenesis, angiogenesis, vascular repair, and tissue engineering, by considering different stem cell sources entailed with osteogenic and angiogenic potential, aimed at collecting the key findings that may enable the development of successful vascularized bone replacements useful in orthopedic and otologic surgery.

Cervical nerve root stimulation. Part I: Technical aspects and normal data

OBJECTIVE

Cervical nerve root stimulation (CRS) is a technique of assessing the proximal segments of motor axons destined to upper extremity muscles. Few studies report normal values. The objective was to determine CMAP onset-latencies and CMAP amplitude, area, and duration changes in healthy controls for the abductor pollicis brevis (APB), abductor digiti minimi (ADM), biceps, and riceps muscles. In addition, to determine the tolerability of CRS, as measured by the visual analog scale (VAS).

METHODS

We studied 21 healthy volunteers prospectively with CRS using four target muscles (APB, ADM, biceps, and triceps) bilaterally. Collision studies were used in all APB recordings. VAS was obtained in all subjects.

RESULTS

Mean CMAP onset-latencies were: APB 14 +/- 1.5 ms; ADM 14.2 +/- 1.5 ms; biceps 5.4 +/- 0.6 ms; triceps 5.4 +/- 1.0 ms. Onset-latency significantly correlated with height for all nerves. The mean change in CMAP amplitude and area (%) between most distal stimulation and CRS was: APB reduction of 15.1 +/- 11.6 and 4.9 +/- 3.6%; ADM reduction of 21.1 +/- 10.7 and 17.2 +/- 8.8; biceps reduction of 10 +/- 11.5 and reduction of 8.7 +/- 6.8; triceps increase of 3.3 +/- 5.2 and 11.0 +/- 9.9% respectively. Mean CMAP duration change between most distal stimulation and CRS was: APB, increase of 20.4 +/- 7.4%; ADM, increase of 14.4 +/- 8.5%; biceps, increase of 13.9 +/- 10.8%; triceps, increase of 7.7 +/- 6.7%. The mean VAS score was 3.8 +/- 1.2, and all subjects completed the study.

CONCLUSIONS

The present study establishes normative data and indicates that CRS is a well-tolerated technique.

SIGNIFICANCE

The normal values may be used as reference data for the needle CRS technique in the assessment of proximal conduction abnormalities.

A case of Lewis–Sumner syndrome with conduction abnormalities only in the brachial plexus and roots

We present a case of subacute weakness of one hand with unusual sensory involvement including the upper thorax. Despite normal distal conduction studies, a clinical diagnosis of Lewis-Sumner syndrome was made and the patient responded well to intravenous immunoglobulins. Repeated studies after clinical exacerbation finally proved the demyelinating nature of the neuropathy using proximal magnetic nerve stimulation. This case underlies the importance of seeking proximal conduction blocks in patients with suspected demyelinating neuropathy.

Magnetic stimulation of the central and peripheral nervous systems

Since 1985, when the technique of transcranial magnetic stimulation (TMS) was first developed, a wide range of applications in healthy and diseased subjects has been described. Comprehension of the physiological basis of motor control and cortical function has been improved. Modifications of the basic technique of measuring central motor conduction time (CMCT) have included measurement of the cortical silent period, paired stimulation in a conditioning test paradigm, repetitive transcranial magnetic stimulation (rTMS), and peristimulus time histograms (PSTH). These methods allow dissection of central motor excitatory versus inhibitory interplay on the cortical motor neuron and its presynaptic connections at the spinal cord, and have proven to be powerful investigational techniques. TMS can be used to assess upper and lower motor neuron dysfunction, monitor the effects of many pharmacological agents, predict stroke outcome, document the plasticity of the motor system, and assess its maturation and the effects of aging, as well as perform intraoperative monitoring. The recent use of rTMS in the treatment of depression and movement disorders is novel, and opens the way for other potential therapeutic applications.

Root stimulation improves the detection of acquired demyelinating polyneuropathies

Thirty-one patients with a presentation compatible with an acquired demyelinating polyradiculoneuropathy were prospectively evaluated for proximal conduction block using root stimulation (RS) of cervical and/or lumbar roots. These same techniques were applied to 78 controls (40 pathological). Proximal conduction block was noted in 20/31 cases and none of the controls. Only 7 of 31 cases met published demyelinating criteria. Intravenous immune globulin therapy was completed by 21/31 patients and 20/21 responded. RS is superior to published electrophysiologic criteria for identifying demyelinating polyneuropathies and predicting who will respond to treatment. RS should be performed in all patients suspected of having an acquired demyelinating polyneuropathy when traditional nerve conduction studies criteria are nondiagnostic. RS reliably predicts those likely to respond to immunosuppressive therapy.

Repetitive magnetic nerve stimulation: technical considerations and clinical use in the assessment of neuromuscular transmission

We assessed to what extent repetitive magnetic stimulation can replace the electrical method. Fifteen healthy subjects and 3 patients with myasthenia gravis were investigated using stimulation of the median, ulnar, axillary and accessory nerves. Single, as well as 3/sec repetitive magnetic and electrical stimuli were applied. When comparing the results of magnetic vs. electrical stimulation, amplitudes, areas and shapes of compound muscle action potentials were not significantly different. Although single magnetic stimuli were much less uncomfortable than the electrical stimuli, differences in comfort were much smaller in the repetitive protocol, because muscular contractions under the magnetic stimulation coil caused unpleasant movements of, for example, the neck. Additional problems arose from technical limitations of the prototype magnetic stimulator used: stimulation intensity was significantly limited, resulting in an inability to elicit supramaximal responses in 11 of the 154 investigations. Overheating of the stimulator coil forced us to give the coil extra time to cool down. These problems might be solved in the future by more focused stimulus geometry and introduction of cooling devices. It is concluded that magnetic stimulation can elicit responses which are equivalent to the electrical method in repetitive nerve stimulation. At present due to some shortcomings it cannot replace electrical stimulation in routine repetitive nerve stimulation.