The mathematical relationship between height and nerve conduction velocity.

Many studies have shown an inverse relationship between axon length (or height) and nerve conduction velocity. A linear relationship was assumed, but there is no physiologic indication the relationship is linear. Furthermore, a linear relationship between height and velocity leads to implausibly low velocities for very long nerves. We propose that power regression analysis would produce more accurate results, in line with physiology. In a power regression the goal is to determine exponent x that best fits the curve V = kLx where k is a constant and L is nerve length. In a previous study, the authors established that the product of conduction time T and energy E or TE = kL3. Mathematical derivation from this relationship yields V2/V1 = (L2/L1)(-0.5), or, velocity V is inversely proportional to the square root of length. Data from 22 normal Ulnar Motor Nerve Conductions showed a very high correlation with this formula (exponent x = -0.529 SE = 0.21, theoretical value -0.5). Data from other researchers also supports this relationship. Overall, Ulnar Motor Nerve Motor Conduction Velocity appears to be inversely proportional to the square root of height. We believe this relationship holds for all long nerves.

A sensitive new median-ulnar technique for diagnosing mild Carpal Tunnel Syndrome.

Carpal Tunnel Syndrome (CTS) is easily the most common focal peripheral nerve compression. The primary diagnostic tool is electrodiagnosis, although 13-27% of patients with symptoms and signs of CTS have normal electrodiagnostic results. The goal of this study was to create a more sensitive and specific latency difference criteria without any additional testing beyond the minimum. Statistical theory indicates that this would occur by comparing the latency most sensitive to CTS to the least sensitive latency. Data was evaluated from 68 normal hands, 23 hands of patients with symptoms and signs of CTS but normal standard results, and 88 hands of patients with CTS symptoms and signs of CTS with the diagnosis confirmed with standard criteria. The Median Sensory latency was the most sensitive parameter, while the Ulnar Motor Latency varied least in the presence of CTS, making the (Median Sensory-Ulnar Motor) latency difference the criteria of choice. Setting a cutoff value of 0.8 msecs for this difference correctly classified all normals, and all hands with CTS by standard criteria, and classified as abnormal 19/23 (82%) of hands with symptoms and signs of CTS but negative results by standard criteria. Overall the (Median Sensory-Ulnar Motor) Latency difference is a simple, easy, sensitive and specific test for CTS.

Treatment of acute deep vein thrombosis in spinal cord injured patients with enoxaparin: a cost analysis.

Enoxaparin, a low molecular weight heparin, has been demonstrated to be effective in the prophylaxis and treatment of deep vein thrombosis (DVT) in the general population. This study presents an analysis of the costs of subcutaneous (SQ) enoxaparin compared with intravenous (IV) heparin. Data were gathered on six spinal cord injured (SCI) patients in an acute freestanding rehabilitation center who were initially treated with SQ enoxaparin (n=3) or IV heparin (n=3) for a proximal DVT. No patients in either group developed further clinical complications. Comparison of the total costs of each treatment was performed, including the direct cost of the drug, as well as some of the costs of administration. Although the cost of enoxaparin per unit dose is higher, the total costs of enoxaparin are slightly lower, because its labor and administration costs are less. Subcutaneous enoxaparin is a safe, cost-effective, and less labor-intensive treatment, and can be of substantial benefit in the treatment of DVT in SCI patients in the rehabilitation setting.

High lumbar disc: diagnostic and treatment dilemma.

The high lumbar disc refers to a disc herniation involving the upper lumbar discs (L2-4). Radiculopathy caused by an upper lumbar disc is occasionally difficult to diagnose secondary to ambiguous presenting symptoms. Once accurately diagnosed, the treatment program is straight-forward but specific for the high nerve root pathology. A series of three cases of high lumbar radiculopathies managed with an aggressive conservative approach are presented. This case series will review the diagnostic and treatment strategies that are useful in the identification and management of a high lumbar radiculopathy. Various pitfalls in the management of these cases are reviewed, all of which may worsen the patient's clinical situation. A high index of suspicion is necessary to elucidate this entity.