Philipp R. Aldana

Incidence and dosimetric parameters of pediatric brainstem toxicity following proton therapy

Abstract Background. Proton therapy offers superior low and intermediate radiation dose distribution compared with photon-based radiation for brain and skull base tumors; yet tissue within and adjacent to the target volume may receive a comparable radiation dose. We investigated the tolerance of the pediatric brainstem to proton therapy and identified prognostic variables. Material and methods. All patients < 18 years old with tumors of the brain or skull base treated from 2007 to 2013 were reviewed; 313 who received > 50.4 CGE to the brainstem were included in this study. Brainstem toxicity was graded according to the NCI Common Terminology Criteria for Adverse Events v4.0. Results. The three most common histologies were ependymoma, craniopharyngioma, and low-grade glioma. Median patient age was 5.9 years (range 0.5–17.9 years) and median prescribed dose was 54 CGE (range 48.6–75.6 CGE). The two-year cumulative incidence of toxicity was 3.8% ± 1.1%. The two-year cumulative incidence of grade 3 + toxicity was 2.1% ± 0.9%. Univariate analysis identified age < 5 years, posterior fossa tumor location and specific dosimetric parameters as factors associated with an increased risk of toxicity. Conclusion. Utilization of current national brainstem dose guidelines is associated with a low risk of brainstem toxicity in pediatric patients. For young patients with posterior fossa tumors, particularly those who undergo aggressive surgery, our data suggest more conservative dosimetric guidelines should be considered.

Flow diversion for complex intracranial aneurysms in young children

Pediatric intracranial aneurysms are exceedingly rare and account for less than 5% of all intracranial aneurysms. Open surgery to treat such aneurysms has been shown to be more durable than endovascular techniques, and durability of treatment is particularly important in the pediatric population. Over the past 2 decades, however, a marked shift in aneurysm treatment from open surgery toward endovascular procedures has occurred for adults. The authors describe their early experience in treating 3 unruptured pediatric brain aneurysms using the Pipeline embolization device (PED). The first patient, a girl with Majewski osteodysplastic primordial dwarfism Type II who was harboring multiple intracranial aneurysms, underwent two flow diversion procedures for a vertebrobasilar aneurysm and a supraclinoid internal carotid artery aneurysm. The second patient underwent PED placement on a previously coiled but enlarging posterior communicating artery aneurysm. All procedures were uneventful, with no postsurgical complications, and led to complete angiographic obliteration of the aneurysms. To the authors knowledge, this is the first series of flow diversion procedures in children reported in the medical literature. While flow diversion is a new and relatively untested technology in children, outcomes in adults have been promising. For challenging lesions in the pediatric population, flow diversion may have a valuable role as a well-tolerated, safe treatment with durable results. Many issues remain to be addressed, such as the durability of flow diverters over a very long follow-up and vessel response to growth in the presence of an endoluminal device.

The naso-axial line: a new method of accurately predicting the inferior limit of the endoscopic endonasal approach to the craniovertebral junction.

BACKGROUND: The endoscopic endonasal approach (EEA) has developed as an emerging surgical corridor to the craniovertebral junction (CVJ). In addition to understanding its indications and surgical anatomy, the ability to predict its inferior limit is vital for optimal surgical planning. OBJECTIVE: To develop a method that accurately predicts the inferior limit of the EEA on the CVJ radiologically and to compare this with other currently used methods. METHODS: Predissection computerized tomographic scans of 9 cadaver heads were used to delineate a novel line, the naso-axial line (NAxL), to predict the inferior EEA limit on the upper cervical spine. A previously described method with the use of the nasopalatine line (NPL or Kassam line) was also used. On computerized tomographic scans obtained following dissection of the EEA, the predicted inferior limits were compared with the actual extent of dissection. RESULTS: The postdissection inferior EEA limit ranged from the dens tip to the upper half of the C2 body, which matched the limit predicted by NAxL, with no statistically significant difference between them. In contrast to the NAxL, the NPL predicted a significantly lower EEA limit (P < .001), ranging from the lower half of the C2 body to the superior end plate of C3. CONCLUSION: The novel NAxL more accurately predicts the inferior limit of the EEA than the NPL. This method, which can be easily used on preoperative sagittal scans, accounts for variations in patients anatomy and can aid surgeons in the assessment of the EEA to address caudal CVJ pathology. ABBREVIATIONS: CVJ, craniovertebral junction EEA, endoscopic endonasal approach HPL, hard palate line NAxL, naso-axial line NPL, nasopalatine line

Ventriculogallbladder shunts in pediatric patients.

OBJECTnThe authors report a clinical protocol for the application of ventriculogallbladder (VGB) shunts in children who may be unable to maintain or receive ventriculoperitoneal (VP) shunts.nnnMETHODSnEighteen patients underwent placement of VGB shunts as an alternative to VP shunt therapy for the following reasons: malfunction of the VP shunt due to suspected failure of the peritoneum to absorb cerebrospinal fluid (17 cases) and multiple intraabdominal general surgical procedures (1 case). The patients ranged in age from 4 months to 17 years (mean 6.5 +/- 6.1 years [standard deviation {SD}]). All patients underwent preoperative imaging of the gall-bladder either by ultrasonography or computed tomography scanning. A team consisting of a pediatric neurological surgeon and a pediatric general surgeon performed all operative procedures. The procedures were conducted by open laparotomy to precisely place the appropriate length of distal catheter and to anchor it to the gallbladder wall.nnnRESULTSnThere were 2 early shunt malfunctions, both obstructions due to sludge (1 in the biliary duct and 1 in the common bile duct). A late-onset (5-year) malfunction occurred secondary to gallbladder stones. In all 3 cases of malfunction, the devices were successfully converted to VP shunts. In 1 patient a conversion to a VP shunt was chosen following a general surgical intervention. There were 2 shunt infections (Staphylococcus epidermidis and Haemophilus influenzae). These were successfully treated. Two patients underwent conversion to a VGB shunt on 2 occasions. Thirteen patients had functional VGB shunts at the time of their last follow-up assessment. The follow-up for these 13 patients ranged from 1 to 8 years (mean 2.1 +/- 2.0 years [SD]).nnnCONCLUSIONSnVentriculogallbladder shunts may be considered for the treatment of hydrocephalus in children when the peritoneal cavity cannot be used as a distal terminus.

The rhinopalatine line as a reliable predictor of the inferior extent of endonasal odontoidectomies.

OBJECTnThe endoscopic endonasal approach (EEA) provides a minimally invasive corridor through which the cervicomedullary junction can be decompressed with reduced morbidity rates compared to those with the classic transoral approaches. The limit of the EEA is its inferior extent, and preoperative estimation of its reach is vital for determining its suitability. The aim of this study was to evaluate the actual inferior limit of the EEA in a surgical series of patients and develop an accurate and reliable predictor that can be used in planning endonasal odontoidectomies.nnnMETHODSnThe actual inferior extent of surgery was determined in a series of 6 patients with adequate preoperative and postoperative imaging who underwent endoscopie endonasal odontoidectomy. The medians of the differences between several previously described predictive lines, namely the nasopalatine line (NPL) and nasoaxial line (NAxL), were compared with the actual surgical limit and the hard-palate line by using nonparametric statistics. A novel line, called the rhinopalatine line (RPL), was established and corresponded best with the actual limit of the surgery.nnnRESULTSnThere were 4 adult and 2 pediatric patients included in this study. The NPL overestimated the inferior extent of the surgery by an average (± SD) of 21.9 ± 8.1 mm (range 14.7-32.5 mm). The NAxL and RPL overestimated the inferior limit of surgery by averages of 6.9 ± 3.8 mm (range 3.7-13.3 mm) and 1.7 ± 3.7 mm (range -2.8 to 8.3 mm), respectively. The medians of the differences between the NPL and NAxL and the actual surgery were statistically different (both p = 0.0313). In contrast, there was no statistically significant difference between the RPL and the inferior limit of surgery (p = 0.4375).nnnCONCLUSIONSnThe RPL predicted the inferior limit of the EEA to the craniovertebral junction more accurately than previously described lines. The use of the RPL may help surgeons in choosing suitable candidates for the EEA and in selecting those for whom surgery through the oropharynx or the facial bones is the better approach.

Ultrasound-aided fixation of a biodegradable cranial fixation system: uses in pediatric neurosurgery

OBJECTnBioresorbable implant systems have been used in neurosurgery for the rigid fixation of cranial and facial bones. A relatively recent advancement has been the fixation of these implants using an ultrasonic device. The experience with such a device in neurosurgical practice has been limited. The authors report on their experience with ultrasound-aided fixation of bioresorbable implants in pediatric neurosurgical practice.nnnMETHODSnThe study consisted of 2 parts. The retrospective portion consisted of a chart review of pertinent clinical information, complications, and outcomes after the use of a commercially available ultrasound-aided bioresorbable implant system (SonicWeld Rx, KLS Martin L.P.). Follow-up was obtained in all patients via clinical examination or telephone interview. The prospective portion of the study consisted of video analysis of the implantation technique in a routine craniotomy. Implantation times were measured, and delays during treatment were noted.nnnRESULTSnOver a period of 2 years, 28 consecutive patients underwent placement of these implants for bone fixation during craniotomies or craniofacial reconstructions. The only complication was seen in a child with Crouzon syndrome, who had a wound infection caused by Serratia sepsis from a central venous line infection. There were no repeated operations for implant-related swelling, and no cases of premature plate resorption, bone instability, or settling. In vivo, the average time required to implant a resorbable pin with this system was 22 seconds.nnnCONCLUSIONSnThe use of a bioresorbable implant system with ultrasound-aided pin fixation in pediatric neurosurgery cases achieved adequate stability with few complications. This system was easy to use and provided rapid fixation of implants.

A treatment planning comparison of highly conformal radiation therapy for pediatric low-grade brainstem gliomas

To the Editor, n nThe brainstem encompasses the midbrain, pons, and medulla. Brainstem gliomas arise at any age, but most frequently occur during childhood. In children, brainstem gliomas constitute approximately 10–20% of the malignancies affecting the central nervous system (CNS) [1], and the average age at diagnosis is 7–9 years with no gender predilection [2,3]. There are approximately 150–300 new cases diagnosed in USA annually [2]. The diagnosis of brainstem glioma includes a histopathologically diverse number of tumor types, which makes it difficult to assign an overall prognosis [4]. Similar to tumors in other CNS sites, however, low-grade brainstem gliomas are curable with current treatment modalities, whereas high-grade gliomas are often fatal despite aggressive treatment [5]. n nOf those children diagnosed with brainstem gliomas, approximately 20% are low-grade gliomas [2,3]. There is variability with regard to the resectability of these tumors; however, in general, complete resection is often impossible [2,3,6–8]. External-beam radiation therapy is an accepted and effective treatment modality for patients with unresectable low-grade brainstem gliomas [1,5–8]. When determining the therapeutic ratio, the risks of radiation therapy must be considered along with the potential benefits [9]. As the best 10-year survival rates mandate a relatively high radiation dose deposited in radiosensitive tissue, children treated for brainstem gliomas with radiation therapy are subject to a number of late sequelae, including hearing loss, neuroendocrine deficits, chronic otitis media, neurocognitive dysfunction, and the development of secondary malignancies [9]. n nThere are few contemporary studies in the literature directly addressing the treatment of low-grade pediatric brainstem gliomas. In general, to minimize the risk of late effects in pediatric patients treated with radiation, investigators have historically sought to attenuate the dose to non-target, healthy tissues. For treatment of low-grade brainstem gliomas, recent studies have sought to investigate the role of gamma knife surgery to reduce dose to non-target tissue [10] and therapies of increased conformality, such as photon-based intensity-modulated radiation therapy (IMRT) and proton therapy [11]. Technology facilitating the delivery of highly conformal radiation therapy, such as IMRT and proton therapy, may allow for better sparing of non-target tissues. In this study, we sought to investigate the relative dosimetric features of photon IMRT and proton therapy in the treatment of low-grade brainstem gliomas in order to assess their potential value in reducing late toxicity.

Clinical outcomes following proton therapy for children with central nervous system tumors referred overseas

International, multidisciplinary care of children with central nervous system (CNS) tumors presents unique challenges. The aim of this study is to report patient outcomes of U.K. children referred for proton therapy to a North American facility.

Ultrasound-aided fixation of biodegradable implants in pediatric craniofacial surgery.

Purpose: Bioresorbable implant systems have been used for the rigid fixation of cranial and facial bones. A relatively recent advancement has been the fixation of these implants using an ultrasonic device. Published reports with such a device in pediatric craniofacial surgery have been limited. We report our experience with ultrasound-aided fixation of bioresorbable implants in the craniofacial surgery of children. Methods: We retrospectively examined the clinical information, complications and outcome following the use of a commercially available ultrasound-aided bioresorbable implant system (SonicWeld Rx™, KLS Martin, Jacksonville, Fla., USA) during craniofacial surgery by University of Florida College of Medicine Jacksonville surgeons. Follow-up was obtained via clinical examination or telephone interview. Results: Over a period of 3 years, 37 pediatric patients (age range: 2 months to 16 years) had placement of these implants for immediate bony fixation during craniofacial procedures. Pathology consisted mainly of craniosynostosis (n = 19), and trauma (n = 16). Twenty-eight had combined craniofacial procedures; 9 patients had facial procedures. Reoperation was performed for: wound infection (n = 1), plate extrusion (n = 1). Delayed subcutaneous plate-related swelling was seen in 5 patients (4 were infants) and had a benign clinical course. Good cosmetic outcomes were seen in all patients. Conclusions: The use of a bioresorbable implant system with ultrasound-aided pin fixation in pediatric craniofacial surgery achieves rapid fixation with minimal morbidity and good cosmetic outcome. This system is easy to use and provides reliable stability in the setting of pediatric trauma and craniosynostosis.

Prioritizing neurosurgical education for pediatricians: results of a survey of pediatric neurosurgeons

OBJECTnPediatricians play a vital role in the diagnosis and initial treatment of children with pediatric neurosurgical disease. Exposure of pediatrics residents to neurosurgical diseases during training is inconsistent and is usually quite limited. After residency, opportunities for pediatricians education on neurosurgical topics are few and fall mainly on pediatric neurosurgeons. The American Association of Neurological Surgery/Congress of Neurological Surgeons Joint Section on Pediatric Neurological Surgery Committee on Education undertook a survey of practicing pediatric neurosurgeons to determine whether focused education of practicing pediatricians might lead to better patient outcomes for children with a sampling of common pediatric neurosurgical conditions.nnnMETHODSnAn Internet-based 40-item survey was administered to practicing pediatric neurosurgeons from the US and Canada identified from the roster of the American Association of Neurological Surgeons/Congress of Neurological Surgeons Joint Section of Pediatric Neurological Surgery. Survey topics included craniosynostosis and plagiocephaly, occult spinal dysraphism and tethered cord, hydrocephalus and endoscopic third ventriculostomy, Chiari malformation Type I, mild or minor head injury, spastic cerebral palsy, and brain tumors. Most questions pertained to diagnosis, initial medical treatment, and referral.nnnRESULTSnOne hundred three (38%) of the 273 practicing pediatric neurosurgeons completed the survey. Two-thirds of the respondents had completed a pediatric neurosurgery fellowship, and two-thirds were in academic practice. Eighty-two percent of the respondents agreed that the care of pediatric neurosurgical patients could be improved with further education of pediatricians. In the opinion of the respondents, the 3 disease topics in greatest need of educational effort were craniosynostosis and plagiocephaly, occult spinal dysraphism and tethered cord, and hydrocephalus. Head injury and spasticity were given the lowest priorities.nnnCONCLUSIONSnThis survey identified what practicing pediatric neurosurgeons perceive to be the most important knowledge deficits of their colleagues in pediatrics. These perceptions may not necessarily be congruent with the perceptions of practicing pediatricians themselves; nevertheless, the data from this survey may serve to inform conversations between neurosurgeons and planners of continuing medical education for pediatricians, pediatrics residency program directors, and medical school pediatrics faculty.