Search Results

You are looking at 1 - 5 of 5 items for

  • Author or Editor: Chandan G. Reddy x
Clear All Modify Search
Full access

Chandan G. Reddy, Goutam G. Reddy, Hiroto Kawasaki, Hiroyuki Oya, Lee E. Miller and Matthew A. Howard III

Object

Control signals for brain-machine interfaces may be obtained from a variety of sources, each with their own relative merits. Electrocorticography (ECoG) provides better spatial and spectral resolution than scalp electroencephalography and does not include the risks attendant upon penetration of the brain parenchyma associated with single and multiunit recordings. For these reasons, subdural electrode recordings have been proposed as useful primary or adjunctive control signals for brain-machine interfaces. The goal of the present study was to determine if 2D control signals could be decoded from ECoG.

Methods

Six patients undergoing invasive monitoring for medically intractable epilepsy using subdural grid electrodes were asked to perform a motor task involving moving a joystick in 1 of 4 cardinal directions (up, down, left, or right) and a fifth condition (“trigger”). Evoked activity was synchronized to joystick movement and analyzed in the theta, alpha, beta, gamma, and high-gamma frequency bands.

Results

Movement-related cortical potentials could be accurately differentiated from rest with very high accuracy (83–96%). Further distinguishing the movement direction (up, down, left, or right) could also be resolved with high accuracy (58–86%) using information only from the high-gamma range, whereas distinguishing the trigger condition from the remaining directions provided better accuracy.

Conclusions

Two-dimensional control signals can be derived from ECoG. Local field potentials as measured by ECoG from subdural grids will be useful as control signals for a brain-machine interface.

Restricted access

Aditya V. Ingalhalikar, Chandan G. Reddy, Tae Hong Lim, James C. Torner and Patrick W. Hitchon

Object

The artificial disc has been proposed as an alternative to spinal fusion for degenerative disc disease. The primary aim of this biomechanical study was to compare motion and intradiscal pressure (IDP) in a ball-and-socket artificial disc–implanted cadaveric lumbar spine, at the operative and adjacent levels, using a displacement-controlled setup. A secondary comparison involved a “salvage” construct, consisting of pedicle screws (PSs) added in supplementation to the artificial disc construct.

Methods

Ten human cadaveric lumbosacral spines (L2–S1) were potted at L-2 and S-1. All measurements were initially made in the intact spine, followed by implantation of the artificial disc, and finally by the salvage PS condition. For the artificial disc condition, a Maverick ball-and-socket artificial disc was implanted at L4–5. For the PS condition, CD Horizon PSs were placed at L4–5, and the artificial disc was left in place. A displacement-controlled, custom-designed testing apparatus was used to impart motion in the sagittal and coronal planes. Motion at both the implanted level (L4–5) and immediately adjacent levels (L3–4 and L5–S1) was measured. Intradiscal pressure at the rostral adjacent level (L3–4) was also measured. The Tukey test was used for statistical analysis (p < 0.05).

Results

In flexion, no significant difference was noted between the artificial disc and the intact spine with regard to motion at the operative level, motion at adjacent levels, or IDP. In lateral bending, while the artificial disc significantly decreased operative-level motion (p < 0.05), no significant difference was noted in adjacent-level motion or IDP. With regard to extension, the artificial disc significantly increased operative level motion and decreased the rostral adjacent level (L3–4) motion and IDP (p < 0.05). Caudal adjacent-level (L5–S1) motion was not significantly different.

In flexion and lateral bending, the addition of PSs significantly decreased motion at the implanted level when compared with the intact spine and the artificial disc (p < 0.05). This decrease in motion at the index level was associated with a compensatory increase in motion at both adjacent levels in flexion only (p < 0.05), but not in lateral bending (p > 0.05). The IDP was significantly increased in lateral bending but not in flexion. With regard to extension, the significant decrease in IDP that was noted with the artificial disc persisted despite the addition of PSs (p < 0.05).

Conclusions

The artificial disc either maintains or reduces adjacent-level motion and pressure, compared with the intact spine. The addition of PSs to the artificial disc construct leads to significantly increased motion at adjacent levels in flexion and significantly increased IDP in lateral bending. At the operative level, the artificial disc is associated with hypermobility in extension, which is restored to the intact state after the addition of supplementary PSs.

Restricted access

Chandan G. Reddy, Nader S. Dahdaleh, Gregory Albert, Fangxiang Chen, Daniel Hansen, Kirill Nourski, Hiroto Kawasaki, Hiroyuki Oya and Matthew A. Howard III

A wide range of devices is used to obtain intracranial electrocorticography recordings in patients with medically refractory epilepsy, including subdural strip and grid electrodes and depth electrodes. Penetrating depth electrodes are required to access some brain regions, and 1 target site that presents a particular technical challenge is the first transverse temporal gyrus, or Heschl gyrus (HG). The HG is located within the supratemporal plane and has an oblique orientation relative to the sagittal and coronal planes. Large and small branches of the middle cerebral artery abut the pial surface of the HG and must be avoided when planning the electrode trajectory.

Auditory cortex is located within the HG, and there are functional connections between this dorsal temporal lobe region and medial sites commonly implicated in the pathophysiology of temporal lobe epilepsy. At some surgical centers, depth electrodes are routinely placed within the supratemporal plane, and the HG, in patients who require intracranial electrocorticography monitoring for presumed temporal lobe epilepsy. Information from these recordings is reported to facilitate the identification of seizure patterns in patients with or without auditory auras.

To date, only one implantation method has been reported to be safe and effective for placing HG electrodes in a large series of patients undergoing epilepsy surgery. This well-established approach involves inserting the electrodes from a lateral trajectory while using stereoscopic stereotactic angiography to avoid vascular injury. In this report, the authors describe an alternative method for implantation. They use frameless stereotaxy and an oblique insertion trajectory that does not require angiography and allows for the simultaneous placement of subdural grid arrays. Results in 19 patients demonstrate the safety and efficacy of the method.

Free access

Chandan G. Reddy, Kimberly K. Amrami, Benjamin M. Howe and Robert J. Spinner

OBJECT

Knee dislocations are often accompanied by stretch injuries to the common peroneal nerve (CPN). A small subset of these injuries also affect the tibial nerve. The mechanism of this combined pattern could be a single longitudinal stretch injury of the CPN extending to the sciatic bifurcation (and tibial division) or separate injuries of both the CPN and tibial nerve, either at the level of the tibiofemoral joint or distally at the soleal sling and fibular neck. The authors reviewed cases involving patients with knee dislocations with CPN and tibial nerve injuries to determine the localization of the combined injury and correlation between degree of MRI appearance and clinical severity of nerve injury.

METHODS

Three groups of cases were reviewed. Group 1 consisted of knee dislocations with clinical evidence of nerve injury (n = 28, including 19 cases of complete CPN injury); Group 2 consisted of knee dislocations without clinical evidence of nerve injury (n = 19); and Group 3 consisted of cases of minor knee trauma but without knee dislocation (n = 14). All patients had an MRI study of the knee performed within 3 months of injury. MRI appearance of tibial and common peroneal nerve injury was scored by 2 independent radiologists in 3 zones (Zone I, sciatic bifurcation; Zone II, knee joint; and Zone III, soleal sling and fibular neck) on a severity scale of 1–4. Injury signal was scored as diffuse or focal for each nerve in each of the 3 zones. A clinical score was also calculated based on Medical Research Council scores for strength in the tibial and peroneal nerve distributions, combined with electrophysiological data, when available, and correlated with the MRI injury score.

RESULTS

Nearly all of the nerve segments visualized in Groups 1 and 2 demonstrated some degree of injury on MRI (95%), compared with 12% of nerve segments in Group 3. MRI nerve injury scores were significantly more severe in Group 1 relative to Group 2 (2.06 vs 1.24, p < 0.001) and Group 2 relative to Group 3 (1.24 vs 0.13, p < 0.001). In both groups of patients with knee dislocations (Groups 1 and 2), the MRI nerve injury score was significantly higher for CPN than tibial nerve (2.72 vs 1.40 for Group 1, p < 0.001; 1.39 vs 1.09 for Group 2, p < 0.05). The clinical injury score had a significantly strong correlation with the MRI injury score for the CPN (r = 0.75, p < 0.001), but not for the tibial nerve (r = 0.07, p = 0.83).

CONCLUSIONS

MRI is highly sensitive in detecting subclinical nerve injury. In knee dislocation, clinical tibial nerve injury is always associated with simultaneous CPN injury, but tibial nerve function is never worse than peroneal nerve function. The point of maximum injury can occur in any of 3 zones.

Free access

Chandan G. Reddy, Oliver E. Flouty, Marshall T. Holland, Leigh A. Rettenmaier, Mario Zanaty and Foad Elahi

OBJECTIVE

Peripheral nerve stimulation (PNS) has been used for the treatment of neuropathic pain for many decades. Despite the specific indications for PNS, clinicians often have difficulty screening for candidates likely to have a good or fair outcome. Given the expense of a permanent implant, most insurance companies will not pay for the implant without a successful PNS trial. And since PNS has only recently been approved by the US Food and Drug Administration, many insurance companies will not pay for a conventional trial of PNS. The objective of this study is to describe a short low-cost method for trialing and screening patients for peripheral nerve stimulator implantation. Additionally, this study demonstrates the long-term efficacy of PNS in the treatment of chronic neuropathic pain and the relative effectiveness of this novel screening method.

METHODS

The records of all patients who had undergone trialing and implantation of a PNS system for chronic refractory pain at the authors' institution over a 1-year period (August 1, 2012–July 31, 2013) were examined in this retrospective case series. The search revealed 17 patients, 13 who had undergone a novel in-office ultrasonography-guided StimuCath screening technique and 4 who had undergone a traditional week-long screening procedure. All 17 patients experienced a successful PNS trial and proceeded to permanent PNS system implantation. Patients were followed up for a mean duration of 3.0 years. Visual analog scale (VAS) pain scores were used to assess pain relief in the short-term (< 6 weeks), at 1 year, and at the last follow-up. Final outcome was also characterized as good, fair, poor, or bad.

RESULTS

Of these 17 patients, 10 were still using their stimulator at the last follow-up, with 8 of them obtaining good relief (classified as ≥ 50% pain relief, with an average 81% reduction in the VAS score) and 2 patients attaining fair relief (< 50% relief but still using stimulation therapy). Among the remaining 7 patients, the stimulator had been explanted in 4 and there had been no relief in 3. Excluding explanted cases, follow-up ranged from 14 to 46 months, with an average of 36 months. Patients with good or fair relief had experienced pain prior to implantation for an average of 5.1 years (range 1.8–15.2 years). A longer duration of pain trended toward a poorer outcome (bad outcome 7.6 years vs good outcome 4.1 years, p = 0.03). Seven (54%) of the 13 patients with the shorter trial experienced a good or fair outcome with an average 79% reduction in the VAS score; however, all 4 of the bad outcome cases came from this group. Three (75%) of the 4 patients with the longer trial experienced a good or fair outcome at the last follow-up, with an average 54% reduction in the VAS score. There was no difference between the trialing methods and the proportion of favorable (good or fair) outcomes (p = 0.71).

CONCLUSIONS

Short, ultrasonography-guided StimuCath trials were feasible in screening patients for permanent implantation of PNS, with efficacy similar to the traditional week-long screening noted at the 3-year follow-up.