Clinical characteristics and electrodiagnostic features in patients with carpal tunnel syndrome, double crush syndrome, and cervical radiculopathy.

Similar unilateral neck and upper limb symptoms are often due to various entrapment neuropathies; carpal tunnel syndrome (CTS) and cervical radiculopathy (CR) are common causes among them. Therefore, we investigated the clinical characteristics and electrodiagnostic features of patients with carpal tunnel syndrome, cervical radiculopathy, and both conditions, called double crush syndrome (DCS). The medical records and electrodiagnostic reports of 866 patients with suspected CTS and CR visited a tertiary-care hospital were retrospectively analyzed. After excluding 101 patients with confounding conditions, 151 (20%) patients were diagnosed to have sole cases of CTS; 362 (47%) patients were diagnosed to have sole cases of CR; 198 (26%) patients were diagnosed to have DCS, while 54 (7%) patients had mere symptoms. Sole cases of CR had the highest incidences of neck pain, upper back pain, wrist and hand weakness. Female patients had the highest incidences of all the diseases in their sixth decade. Male patients had comparably distinguished high occurrence of all the diseases in their fifth to sixth decades. Although comparison of nerve conduction studies between patients with mere symptoms and patients with sole cases of CTS or DCS showed statistical differences, comparison between the latter two revealed no difference. We found most patients referred for electrodiagnostic studies had cervical radiculopathy. High concomitant occurrence of CTS and CR suggests cautious evaluation of patients with upper limb symptoms is important, because the management of these conditions is quite different.

A computational study of the flow through a vitreous cutter.

Vitrectomy is an ophthalmic microsurgical procedure that removes part or all of the vitreous humor from the eye. The procedure uses a vitreous cutter consisting of a narrow shaft with a small orifice at the end through which the humor is aspirated by an applied suction. An internal guillotine oscillates back and forth across the orifice to alter the local shear response of the humor. In this work, a computational study of the flow in a vitreous cutter is conducted in order to gain better understanding of the vitreous behavior and provide guidelines for a new vitreous cutter design. The flow of a Newtonian surrogate of vitreous in a two-dimensional analog geometry is investigated using a finite difference-based immersed boundary method with an algebraically formulated fractional-step method. A series of numerical experiments is performed to evaluate the impact of cutting rate, aspiration pressure, and opening/closing transition on the vitreous cutter flow rate and transorifice pressure variation during vitrectomy. The mean flow rate is observed to increase approximately linearly with aspiration pressure and also increase nearly linearly with duty cycle. A study of time-varying flow rate, velocity field, and vorticity illuminates the flow behavior during each phase of the cutting cycle and shows that the opening/closing transition plays a key role in improving the vitreous cutter's efficacy and minimizing the potential damage to surrounding tissue. The numerical results show similar trend in flow rate as previous in vitro experiments using water and balanced saline solution and also demonstrate that high duty cycle and slow opening/closing phases lead to high flow rate and minor disturbance to the eye during vitrectomy, which are the design requirements of an ideal vitreous cutter.