The purpose of this study was to describe microsurgical anatomy of the dorsal root entry zone (DREZ) and provide an anatomic basis for the approach of DREZ lesion in treating radiculopathy of brachial plexus avulsion injuries. We studied 100 dorsal cervical roots and DREZ/ posterior horn complexes in 20 adult cadavers. At each root level the following data were recorded: widths of laminectomy, numbers of posterior rootlets, angle of the inferior rootlets with the spinal cord, and distance from posterior median sulcus to posterolateral sulcus. On cross-sectional plane, the length and width of dorsal horn and the angle between longitudinal axis of dorsal horn and sagittal plane of spinal cord were measured. The results showed that the spinal cord segment and the entry of dorsal roots from C5 to T1 were exposed clearly after laminectomy from C4 to C7. The average number of roolets of C5-T1 roots was about 7.76 and C6 has the most. From up to down, the angle from the inferior rootlet to spinal cord of C5-T1 diminished gradually. The average distance from posterior median sulcus to posterolateral sulcus was 2.95 mm. The average length, width, and angle of posterior horn were 3.47 mm, 1.346 mm, and 35.98, respectively. Our study demonstrated that the spinous process and lamina of the C4 to C7 vertebrae should be resected to expose the C5-T1 when DREZ lesions are employed to treat pain after brachial plexus avulsion. The lesion-making apparatus should be inserted at an angle of 308-408, the width of lesion should be less than 1.2 mm and the lesion depth less than 3.1 mm. Deafferentation pain is a common complication of brachial plexus avulsion injuries. It is reported that the incidence of severe pain after brachial plexus avulsion is 25-90%. 1-3 In a 3-year follow-up of 122 patients of brachial plexus avulsion injuries, Wynn-Parry found that one-third reported residual pain severe enough to affect their daily activities. 4 In 1972, Sindou et al. performed the first dorsal root entry zone (DREZ) microsurgical operation by creating a lesion in the DREZ to treat spasticity and pain. 5,6 Since then, this procedure was adopted by many centers to treat intractable pain syndromes, such as brachial plexus avulsion pain, trigeminal nerve pain, post-herpetic pain, phantom pain, cancer pain involved nerve, end-zone pain post, etc. 7-11 Series of DREZ lesions can also be produced with microsurgical lasers, ultrasonic, and computer-assisted microcoagulation. [12][13][14][15][16] At present, the DREZ lesion has been accepted as one of the most effective procedures in relieving the intractable deafferentation pain in patients with brachial plexus avulsion and spinal injuries. Successful pain relief occurs in 75-80% of patients and more than 72% of patients with brachial plexus avulsion injuries obtained long-term pain relief in a 2-to10-year follow-up study. 17,18 However, the procedure of creating a lesion in the DREZ carries some complications. 19,11 If the DREZ were not completely ablated, the outcome of pain relief might not be ...

We investigate the target and intensity dependence of plateau in high-order above threshold ionization (HATI) by simulating the two-dimensional (2D) momentum distributions and the energy spectra of photoelectrons in HATI of rare gas atoms through using the quantitative rescattering model. The simulated results are compared with the existing experimental measurements. It is found that the slope of the plateau in the HATI photoelectron energy spectrum highly depends on the structure of elastic scattering differential cross section (DCS) of laser-induced returning electron with its parent ion. The investigations of the long- and short-range potential effects in the DCSs reveal that the short-range potential, which reflects the structure of the target, plays an essential role in generating the HATI photoelectron spectra.