Mark A. Mahan

Evaluation of operative procedures for symptomatic outcome after decompression surgery for Chiari type i malformation

The wide spectrum of symptoms and radiographic findings in patients with Chiari I malformation makes the decision to proceed with intervention controversial. We evaluated symptomatic outcomes using diverse surgical techniques in 104 patients who underwent decompression surgery. The symptoms of most patients improved. Patients with syringomyelia showed less symptomatic improvement; however, syringomyelia was not associated with postoperative symptomatic worsening. Durotomy was performed in 97.1% and arachnoid opening was performed in 60.6% with visualization of the fourth ventricle in 51.9% of patients. Neither arachnoid opening nor fourth ventricle visualization was associated with the clinical outcome. Duraplasty was performed in 94.2% of patients. A Chiari plate was used in 13.4% of patients and was associated with favorable outcomes. Use of postoperative steroids or muscle relaxants was not associated with outcome. Syringomyelia showed a 62.5% improvement rate on postoperative MRI. In conclusion, bony decompression and dural opening are important aspects of Chiari I surgery, with symptomatic improvement observed in most patients.

Electromagnetic stereotactic navigation for external ventricular drain placement in the intensive care unit

Placement of external ventricular drains subjects patients to risks of injury, intracerebral hematoma, and failure from improper placement. Traditional free-hand placement has been associated with a relatively frequent occurrence of these complications. We sought to assess the accuracy of ventriculostomy when performed using image-navigation technology in the intensive care unit (ICU). Thirty-five patients were consecutively enrolled in a single-arm trial evaluating the accuracy and complications from ventriculostomies performed at the ICU bedside using electromagnetic image guidance technology. The duration of any additional imaging and the length of the total procedure were also quantified. There were no unacceptably placed ventriculostomy catheters; only two catheters were not perfectly placed in the ipsilateral frontal horn. There was only one patient with tract hemorrhage. The use of image guidance technology added approximately 36 minutes to the time from when the need was identified to when successful drainage was achieved (p = 0.002), but added only 4 minutes of operative time (p = 0.12). Accuracy of placement demonstrated a statistically significant improvement in the accuracy of ventriculostomy over historical data. There were two registration failures which were converted to the traditional technique; there were no other complications arising from the use of image-guided technology. Electromagnetic image guidance is feasible and accurate. Image guidance technology eliminated unacceptably placed catheters and may reduce the risk of catheter-associated intracerebral hemorrhages.

Fibroproliferative neuromas may occur after iatrogenic injury for lipomatosis of nerve.

BACKGROUNDnLipomatosis of nerve (LN) is a condition associated with nerve-territory overgrowth. We have noted a unique type of neuroma at sites of LN injury; the neuroma extends beyond the epineurium, enhances, and appears to enlarge over time.nnnOBJECTIVEnWe sought to understand the relationship between fibroproliferative scarring and surgery performed on the nerve.nnnMETHODSnA review of the searchable records for LN at our institution found 52 cases, confirmed by pathology or pathognomonic appearance on magnetic resonance imaging (MRI). Clinical histories were reviewed to categorize the surgeries performed by the degree of iatrogenic injury to the nerve. Postoperative MRI was performed in 22 of the 46 patients who had surgery, which was then retrospectively reviewed for fibroproliferative neuromas.nnnRESULTSnComplex and masslike neuromas were found on MRI, correlating with the degree of iatrogenic injury to the nerve. These fibrous neuromas proliferated beyond the epineurium, disrupted fascicular architecture, were contrast enhancing when contrast was administered, indicative they were unique and unlike stump or traction neuromas. Of the 8 patients who underwent surgery involving nerve decompression alone, none developed fibroproliferative neuromas. Of the 7 patients who underwent surgery involving nerve debulking, fibroproliferative neuromas developed in 4. Of the 11 patients who underwent surgery involving nerve transection, all developed fibroproliferative neuromas (P < .001). There was also a high incidence of hypertrophic scarring of the skin incision (21.3%).nnnCONCLUSIONnSurgical injury of LN appears to be strongly associated with the development of fibroproliferative neuromas. It is possible that the pathological overgrowth stimulus associated with LN promotes exuberant scar formation.

Long-Term Progression of Lipomatosis of Nerve

OBJECTIVEnLipomatosis of nerve (LN) is a condition of massive peripheral nerve enlargement due to proliferation of fibrous and adipose tissue within the nerve, the natural history of which is currently unknown. We measured the pattern of growth in individuals with long-term radiologic follow-up.nnnMETHODSnReview of the searchable records for LN at our institution found 52 patients, confirmed by pathology or pathognomic appearance on MRI. Ten patients had serial MRI of the same anatomic region for more than 2 years of clinical follow-up. Volumetric analysis was performed using regions of interest on serially imaged segments of affected nerves. Adjustment for skeletal growth was performed for pediatric patients.nnnRESULTSnLN enlarged in 7 of 10 individuals, often both longitudinally along the nerve and in cross-sectional volume. Regarding cross-sectional volume, 2 of the 10 patients demonstrated volume growth more than doubling and 5 additional patients had a >20% increase in nerve volume; the remaining 3 patients were quiescent, where change in the nerve volume was within the error range of volumetric analysis. All cases with growth remained >20% after adjustment for skeletal growth. Five of 10 individuals had longitudinal extension, even with correction for skeletal growth. More significant growth was noted in younger patients (P=0.02). Growth rates more than 5% per year correlated with surgery, without statistical significance in this small population (P=0.14).nnnCONCLUSIONSnSerial MRI reveals progressive enlargement of LN. The rate of growth was more profound in youth, but also occurred in early adulthood.

Robot-assisted triple neurectomy for iatrogenic inguinal pain: a technical note

BackgroundPainful neuromas are a relatively common complication of hernia and abdominal wall surgery.ObjectiveSurgical neurectomy has the potential to to provide durable relief for chronic pain; however, current surgical approaches are not without morbidity or anatomical challenges.We sought a surgical alternative.Methods In the treatment of a case of incapacitating inguinal pain, we performed an anterior transperitoneal approach using a surgical robot.ResultsThis approach was facile and provided elegant anatomical visualization.ConclusionThis case describes the first known robot-assisted laparoscopic triple neurectomy and details a simplified, transperitoneal approach.

Pharmacophysiology of bone and spinal fusion

BACKGROUND CONTEXTnIn recent years, the number of complex spinal surgeries has increased significantly in the elderly population, where the prevalence of low bone density is highest. Consequently, spine surgeons often treat osteoporotic patients who are associated with higher rates of instrumentation failure. Therefore, establishing a successful fusion requires an appropriate substrate for bone formation and local bone remodeling. The fusion process can be supported by therapies that seek to shift the balance of bone homeostasis to increased formation and reduced resorption.nnnPURPOSEnThorough understanding of the physiology of bone formation and adjunctive therapies can help improve fusion rates. Therefore, we present a thorough review of the latest pharmacologic agents used to enhance bone strength and surgical spinal fusion.nnnMETHODSnSystematic review of literature.nnnRESULTSnCurrent knowledge on bone physiology has led to the development of several pharmacologic agents that enhance bone formation and strengthen the human skeleton. At present, natural supplements of vitamin D and calcium or synthetic medications like bisphosphonates are widely used before and after spine surgeries to enhance bone fusion. Additional physiologic agents, including testosterone, parathyroid hormone, calcitonin, and growth hormone, have been shown to improve bone mass density or spinal fusion in both animal and human studies. As in other medical fields, gene therapy has shown viability and promise with the use of both viral and nonviral vectors.nnnCONCLUSIONSnThrough the understanding of bone physiology, numerous natural and synthetic pharmacologic agents have been developed to enhance the bodys skeleton and to improve outcomes of spinal fusion surgery.

Occult radiological effects of lipomatosis of the lumbosacral plexus

ObjectiveLipomatosis of nerve (LN) is a condition of massive peripheral nerve enlargement frequently associated with hypertrophy within the distribution of the nerve, and most commonly affecting the distal limbs. We sought to understand if LN of the lumbosacral plexus would be associated with the trophic effects of LN on surrounding tissue within the pelvis, which may be clinically occult, but present on MRI.Materials and MethodsFifty-one cases of LN, confirmed by pathology or pathognomonic appearance on MRI, were reviewed. Patients with LN of the sciatic nerve were investigated for radiological signs suggestive of overgrowth.ResultsFive patients had involvement of the sciatic nerve, 4 of whom had MR imaging of the pelvis. Three patients had LN involving the lumbosacral plexus, and one patient had isolated involvement of the sciatic nerve. All patients with involvement of the lumbosacral plexus demonstrated previously unrecognized evidence of nerve territory overgrowth in the pelvis, including: LN, profound adipose proliferation, muscle atrophy and fatty infiltration, and bone hypertrophy and ankylosis. The patient with LN involving the intrapelvic sciatic nerve, but not the lumbosacral plexus did not demonstrate any radiological evidence of pelvic overgrowth.ConclusionLN is broader in anatomical reach than previously understood. Proximal plexal innervation may be involved, with a consequent effect on axial skeleton and intrapelvic structures.

Anesthesia Considerations for Monitoring TCMEPs in Adults Diagnosed with Poliomyelitis as Children: A Case Report

ABSTRACT. The use of transcranial motor evoked potentials (TCMEPs) to detect and hopefully prevent injury to the brain, spinal cord, and peripheral nerves intraoperatively has increased greatly in recent years. It is well established that in addition to certain anesthetic agents, patient factors such as advanced age, obesity, diabetes, hypertension, and a collection of neurological and neuromuscular diseases and disorders can greatly reduce or completely eliminate the ability to monitor TCMEPs effectively. One such disease, poliomyelitis (polio), is a highly contagious viral disease that has been mostly forgotten since its near-eradication through vaccination. Over the past three decades there has been increasing recognition of late onset neurological deterioration in individuals who were afflicted by, and apparently recovered from, paralytic poliomyelitis much earlier in life. This condition is known as post-poliomyelitis syndrome (PPS). Patients that appear to have fully recovered from polio, and those with PPS, may require special anesthetic considerations to facilitate effective TCMEP monitoring. Case Report: We report the rapid loss of only lower extremity TCMEPs bilaterally during a C6-C7, C7-T1 ACDF in a 67-year-old female to treat left-sided C7-C8 radiculopathy and C6-T1 foraminal stenosis. The general anesthetic maintenance regimen of 0.3 MAC sevoflurane and 100 μg/kg/min propofol was paused, and a wake-up test was initiated. Full upper and lower extremity motor function was observed. A thorough review of the patients medical history revealed the potential risk factor of full recovery from poliomyelitis as a child. The sevoflurane was removed from the anesthetic regimen, and the lower extremity TCMEPs returned and were present for the remainder of the surgery.

Traumatic intraneural bone fracture fragment.

Intraneural bone was identified on pathologic examination of a neuroma-in-continuity resected for repair of the suprascapular nerve 4 months after a brachial plexus injury. The acute onset of the neurologic deficit, the location of the neuroma within the scapular notch, and the proximity of the neural pathology to a comminuted scapula fracture suggest traumatic penetration of the nerve by a bone fragment. To the authors knowledge, the observation of bone within a neuroma has not been previously reported.

Minimally Invasive Management of Complications from Previous Midline Spinal Surgery

Study background: The application of MIS techniques to address complications of previous midline surgery has not been fully explored. nMethods: Three patients with previous midline lumbar surgery underwent revision surgery with minimally invasive approaches for management of either: infection, recurrent radiculopathyor symptomatic heterotopic bone formation. nResults: Patient 1 was found to have a persistent discitis 10 months after a lumbar fusion that was complicated by a pseudoarthrosis and infection requiring a second surgery for additional stabilization and third surgery for an incision and drainage. To avoid reopening the incision for a fourth time, a minimally invasive retractor was used to access the disc space and remove the interbody spacer. Patient 2 experienced a recurrent radiculopathy three months after an L5-S1 transforaminal lumbar interbody fusion. CT scan demonstrated heterotopic bone formation into the S1 neural foramen. A minimally invasive retractor was used through a paramedian incision to explant the pedicle screw rod construct on the symptomatic side, remove the heterotopic bone formation and decompress the neural foramen. Patient 3 experienced onset of an S1 radiculopathy 11 years after an L4 to S1 fusion. A fixed tubular minimally invasive retractor was used to access the S1 neural foramen and decompress the symptomatic root. nConclusions: Minimally invasive spinal surgical techniques have the capacity to adequately address focal complications that have occurred with midline surgery. These techniques preclude the need to reopen a previous incision, which is especially valuable in those patients with delayed healing capacity, extensive previous surgery or previous infection.