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Krishna Kumar, Rahul Nath, and Gordon M. Wyant

✓ Epidural spinal cord stimulation by means of chronically implanted electrodes was carried out on 121 patients with pain of varied benign organic etiology. In 116 patients, the pain was confined to the back and lower extremities and, of these, 56 exhibited the failed-back syndrome. Most patients were referred by a pain management service because of failure of conventional pain treatment modalities. Electrodes were implanted at varying sites, dictated by the location of pain. A total of 140 epidural implants were used: 76 unipolar, 46 Resume electrodes, 12 bipolar, and six quadripolar. Patients were followed for periods ranging from 6 months to 10 years, with a mean follow-up period of 40 months. Forty-eight patients (40%) were able to control their pain by neurostimulation alone. A further 14 patients (12%), in addition to following a regular stimulation program, needed occasional analgesic supplements to achieve 50% or more relief of the prestimulation pain. Pain secondary to arachnoiditis or perineural fibrosis following multiple intervertebral disc operations, when predominantly confined to one lower extremity, seemed to respond favorably to this treatment. Uniformly good results were also obtained in lower-extremity pain secondary to multiple sclerosis. Pain due to advanced peripheral vascular disease of the lower limbs was well controlled, and amputation below the knee was delayed for up to 2 years in some patients. Pain due to cauda equina injury, paraplegic pain, phantom-limb pain, pure midline back pain without radiculopathy, or pain due to primary bone or joint disease seemed to respond less well. Patients who responded to preliminary transcutaneous electrical nerve stimulation generally did well with electrode implants. Notable complications included wound infection, electrode displacement or fracturing, and fibrosis at the stimulating tip of the electrode. Three patients in this series died due to unrelated causes. Epidural spinal cord stimulation has proven to be an effective and safe means of controlling pain on a long-term basis in selected groups of patients.

The mechanism of action of stimulation-produced analgesia remains unclear; further studies to elucidate it might allow spinal cord stimulation to be exploited more effectively in disorders that are currently refractory to this treatment modality.

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David S. Hersh, Rahul Kumar, Paul Klimo Jr., Markus Bookland, and Jonathan E. Martin

OBJECTIVE

Late failure is a well-documented complication of cerebrospinal fluid shunt placement and, less commonly, endoscopic third ventriculostomy (ETV). However, standards regarding the frequency of clinical and radiological follow-up in these patients have not been defined. Here, the authors report on their survey of surgeons at sites for the Hydrocephalus Clinical Research Network (HCRN) or its implementation/quality improvement arm (HCRNq) to provide a cross-sectional overview of practice patterns.

METHODS

A 24-question survey was developed using the Research Electronic Data Capture (REDCap) platform and was distributed to the 138 pediatric neurosurgeons across 39 centers who participate in the HCRN or HCRNq. Survey questions were organized into three sections: 1) Demographics (5 questions), 2) Shunt Surveillance (12 questions), and 3) ETV Surveillance (7 questions).

RESULTS

A total of 122 complete responses were obtained, for an overall response rate of 88%. The majority of respondents have been in practice for more than 10 years (58%) and exclusively treat pediatric patients (79%). Most respondents consider hydrocephalus to have stabilized 1 month (21%) or 3 months (39%) after shunt surgery, and once stability is achieved, 72% then ask patients to return for routine clinical follow-up annually. Overall, 83% recommend lifelong clinical follow-up after shunt placement. Additionally, 75% obtain routine imaging studies in asymptomatic patients, although the specific imaging modality and frequency of imaging vary. The management of an asymptomatic increase in ventricle size or an asymptomatic catheter fracture also varies widely. Many respondents believe that hydrocephalus takes longer to stabilize after ETV than after shunt placement, reporting that they consider hydrocephalus to have stabilized 3 (28%), 6 (33%), or 12 (28%) months after an ETV. Although 68% of respondents have patients return annually for routine clinical follow-up after an ETV, only 56% recommend lifelong follow-up. The proportion of respondents who perform lifelong follow-up increases with greater practice experience (p = 0.01). Overall, 67% of respondents obtain routine imaging studies in asymptomatic patients after an ETV, with “rapid” MRI the study of choice for most respondents.

CONCLUSIONS

While there is a general consensus among pediatric neurosurgeons across North America that hydrocephalus patients should have long-term follow-up after shunt placement, radiological surveillance is characterized by considerable variety, as is follow-up after an ETV. Future work should focus on evaluating whether any one of these surveillance protocols is associated with improved outcomes.

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Krishna Kumar, Cory Toth, Rahul K. Nath, Ashok K. Verma, and John J. Burgess

✓ Spinal cord stimulation was used in 46 patients for pain associated with lower extremity ischemic vascular disease that was considered to be nonreconstructable. Thirty-nine patients who had a follow-up examination between 2 and 36 months after the procedure form the basis of this report. Thirty (77%) of 39 cases were considered successful. Clinical endpoints indicating failure included amputation, vascular reconstruction, poor pain relief, or hardware malfunction. The transcutaneous partial pressure of oxygen (TcPO2) increased in both target and control feet. In patients with good outcome with a preimplantation TcPO2 of less than 30 mm Hg, TcPO2 increased significantly (p < 0.05). Pulse volume recording improved significantly (p < 0.05) at the thigh, metatarsal, and great toe levels in successfully treated patients. Peak blood flow velocity also showed a significant increase in patients with good outcome (p < 0.05). Patients with a TcPO2 of less than 10 mm Hg following stimulation tended to undergo amputation within the first 3 months.

Improvement in pain control, combined with an increase in TcPO2 values that was greater than 10 mm Hg, were significant early predictors of long-term success. An initial increase in peak blood flow velocities (measured in Doppler studies) of greater than 10 mm also signified a good long-term outcome. Spinal cord stimulation appears to be a useful therapeutic modality for controlling pain and improving perfusion in a select group of patients with end-stage ischemic vascular disease considered nonreconstructable. The best results were seen in patients with severe claudication and rest pain without trophic changes in the foot. The mechanism of this beneficial effect is not yet completely understood.

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Rahul Kumar, David S Hersh, Luke G. F Smith, William E Gordon, Nickalus R Khan, Andrew J Gienapp, Busra Gungor, Michael J Herr, Brandy N Vaughn, L. Madison Michael II, and Paul Klimo Jr.

OBJECTIVE

Neurosurgical residents receive exposure to the subspecialty of pediatric neurosurgery during training. The authors sought to determine resident operative experience in pediatric neurosurgery across Accreditation Council for Graduate Medical Education (ACGME)–accredited neurosurgical programs.

METHODS

During 2018–2019, pediatric neurosurgical case logs for recent graduates or current residents who completed their primary pediatric exposure were collected from US continental ACGME training programs. Using individual resident reports and procedure designations, operative volumes and case diversity were analyzed collectively, according to training site characteristics, and also correlated with the recently described Resident Experience Score (RES).

RESULTS

Of the 114 programs, a total of 316 resident case logs (range 1–19 residents per program) were received from 86 (75%) programs. The median cumulative pediatric case volume per resident was 109 (IQR 75–161). Residents at programs with a pediatric fellowship reported a higher median case volume (143, IQR 96–187) than residents at programs without (91, IQR 66–129; p < 0.0001). Residents at programs that outsource their pediatric rotation had a lower median case volume (84, IQR 52–114) compared with those at programs with an in-house experience (117, IQR 79–170; p < 0.0001). The case diversity index among all programs ranged from 0.61 to 0.80, with no statistically significant differences according to the Accreditation Council for Pediatric Neurosurgery Fellowships designation or pediatric experience site (p > 0.05). The RES correlated moderately (r = 0.44) with median operative volumes per program. A program’s annual pediatric operative volume and duration of pediatric experience were identified as significant predictive factors for median resident operative volume.

CONCLUSIONS

Resident experience in pediatric neurosurgery is variable within and between programs. Case volumes are generally higher for residents at programs with in-house exposure and an accredited fellowship, but case diversity is relatively uniform across all programs. RES provides some insight on anticipated case volume, but other unexplained factors remain.

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Krishna Kumar, Rahul K. Nath, C. P. V. Nair, and S. P. Tchang

✓ The authors present a case of thoracic spinal cord compression secondary to epidural lipomatosis in an obese patient. This patient represents the 10th case of epidural lipomatosis secondary to simple obesity reported in the literature. The diagnosis is based on three criteria: 1) medical history and physical examination consistent with segmental spinal cord compression; 2) epidural fat thickness greater than 7 mm in the region of compression, based on magnetic resonance imaging (preferred) or computerized tomographic imaging; and 3) a height-to-weight ratio greater than 27.5 kg/m2. This specific correlation between epidural fat thickness measurement and calculation of height-to-weight ratio has not previously been reported.

Surgical decompression through a posterior laminectomy and excision of excess epidural fat resulted in immediate reversal of the patient's symptoms. Knowledge of the association of epidural lipomatomis with obesity in the absence of glucocorticoid imbalance is important in discerning what may be an underrecognized syndrome.

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David S. Hersh, Rahul Kumar, Kenneth A. Moore, Luke G. F. Smith, Christopher L. Tinkle, Jason Chiang, Zoltan Patay, Amar Gajjar, Asim F. Choudhri, Jorge A. Lee-Diaz, Brandy Vaughn, and Paul Klimo Jr.

OBJECTIVE

Biopsies of brainstem lesions are performed to establish a diagnosis in the setting of an atypical clinical or radiological presentation, or to facilitate molecular studies. A better understanding of the safety and diagnostic yield of brainstem biopsies would help guide appropriate patient selection.

METHODS

All patients who underwent biopsy of a brainstem lesion during the period from January 2011 to June 2019 were reviewed. Demographic, radiological, surgical, and outcome data were collected.

RESULTS

A total of 58 patients underwent 65 brainstem biopsies during the study period. Overall, the median age was 7.6 years (IQR 3.9–14.2 years). Twenty-two of the 65 biopsies (34%) were open, 42 (65%) were stereotactic, and 1 was endoscopic. In 3 cases (5%), a ventriculoperitoneal shunt was placed, and in 9 cases (14%), a posterior fossa decompression was performed during the same operative session as the biopsy. An intraoperative MRI (iMRI) was performed in 28 cases (43%). In 3 of these cases (11%), the biopsy was off target and additional samples were obtained during the same procedure. New neurological deficits were noted in 5 cases (8%), including sensory deficits, ophthalmoparesis/nystagmus, facial weakness, and hearing loss; these deficits persisted in 2 cases and were transient in 3 cases. A pseudomeningocele occurred in 1 patient; no patients developed a CSF leak or infection. In 8 cases (13%) an additional procedure was needed to obtain a diagnosis.

CONCLUSIONS

Brainstem biopsies are safe and effective. Target selection and approach should be a collaborative effort. iMRI can be used to assess biopsy accuracy in real time, thereby allowing any adjustment if necessary.