Handbook of Pediatric Neurosurgery

Handbook of Pediatric Neurosurgery 1st Edition

by George I. Jallo (Editor), Karl Kothbauer (Editor), Violette Recinos (Editor)

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Pediatric neurosurgery has witnessed considerable technological advances, resulting in more efficacious outcomes for young patients with hydrocephalus, epilepsy, brain tumors, spinal deformities, and a host of other conditions. The art of pediatric neurosurgery is a delicate balancing act—taking into account child and parents and emotional and disease challenges. As such, the management of serious neurological conditions in pediatric patients must encompass the big picture in addition to treating underlying pathologies.

Handbook of Pediatric Neurosurgery by George Jallo, Karl Kothbauer, and Violette Recinos covers the full depth and breadth of this uniquely rewarding subspecialty including congenital, developmental, and acquired disorders. The latest information is provided on anatomy, radiological imaging, and principles guiding the surgical and nonsurgical management of a full spectrum of neurological pathologies impacting infants and children. The book is divided into 11 sections and 56 chapters with state-of-the-art procedures, best practices, and clinical pearls from top pediatric neurosurgeons.

Key Features

Cranial disorders including Chiari malformations, encephaloceles, Dandy-Walker malformation, and craniosynostosis
Benign and malignant tumors—from the hypothalamus and optic pathways to the brainstem and spinal column
Spinal abnormalities such as spina bifida, tethered cord, and scoliosis
Clinical questions and answers at the end of chapters—ideal for self-testing and exam prep
Comprehensive and compact, this is the perfect backpack reference for neurosurgery residents and pediatric neurosurgery fellows to carry on rounds. It is also a must-have resource for seasoned pediatric neurosurgeons and all practitioners entrusted with the neurological care of pediatric patients.

Update: Posttraumatic epilepsy in children

Posttraumatic epilepsy in children

Posttraumatic epilepsy (PTE) after a traumatic brain injury occurs in 10%-20% of children.

Among children with moderate traumatic brain injury or severe traumatic brain injury, the presence of additional CT findings, other than skull fractures, seem to increase the risk of PTE. In the cohort of Keret et al, the occurrence of an early seizure did not confer an increased risk of PTE 1).

Mild traumatic brain injury (MTBI) was found to confer increased risk for the development of PTE and intractable PTE, of 4.5 and 8 times higher, respectively. As has been established in adults, these findings confirm that MTBI increases the risk for PTE in the pediatric population 2).

There is a a need for biomarkers in children following traumatic brain injury to reliably evaluate the risk of post-traumatic epilepsy 3).

Classification

Literature recognizes several posttraumatic seizure subtypes based on time of presentation and the underlying pathophysiology: impact, immediate, delayed early, and late/posttraumatic epilepsy. Appropriate classification of pediatric posttraumatic seizure subtypes can be helpful for appropriate management and prognosis.

A review of Arndt et al focused on early posttraumatic seizures, and the subtypes of early posttraumatic seizure. Incidence, risk factors, diagnosis, seizure semiology, status epilepticus, management, risk of recurrence, and prognosis were reviewed. The integration of continuous electroencephalographic (EEG) monitoring into pediatric traumatic brain injury management may hold the key to better characterizing and understanding pediatric early posttraumatic seizures 4).

Treatment

The aim of a rapid evidence review was to provide a synthesis of existing evidence on the effectiveness of treatment interventions for the prevention of PTE in people who have suffered a moderate/severe TBI to increase awareness and understanding among consumers. Electronic medical databases (n = 5) and gray literature published between January 2010 and April 2015 were searched for studies on the management of PTE. Twenty-two eligible studies were identified that met the inclusion criteria. No evidence was found for the effectiveness of any pharmacological treatments in the prevention or treatment of symptomatic seizures in adults with PTE. However, limited high-level evidence for the effectiveness of the antiepileptic drug levetiracetam was identified for PTE in children. Low-level evidence was identified for nonpharmacological interventions in significantly reducing seizures in patients with PTE, but only in a minority of cases, requiring further high-level studies to confirm the results 5).

Case series

2018

During a median follow-up period of 7.3 years, 9 (9%) of 95 children with moderate-to-severe TBI developed PTE; 4 developed intractable epilepsy. The odds for developing PTE was 2.9 in patients with severe compared to moderate TBI. CT findings showed fractures in 7/9 (78%) of patients with PTE, compared to 40/86 (47%) of those without PTE (p = 0.09). Of the patients with fractures, all those with PTE had additional features on CT (such as haemorrhage, contusion and mass effect), compared to 29/40 (73%) of those without PTE. One of nine (11%) PTE patients and 10 of 86 (12%) patients without PTE had immediate seizures. Two (22%) children with PTE had their first seizure more than 2 years after the TBI.

Among children with moderate or severe TBI, the presence of additional CT findings, other than skull fractures, seem to increase the risk of PTE. In this cohort, the occurrence of an early seizure did not confer an increased risk of PTE 6).

2017

Data were collected from electronic medical records of children 0-17 years of age, who were admitted to a single medical center between 2007 and 2009 with a diagnosis of MTBI. This prospective research consisted of a telephone survey between 2015 and 2016 of children or their caregivers, querying for information about epileptic episodes and current seizure and neurological status. The primary outcome measure was the incidence of epilepsy following TBI, which was defined as ≥ 2 unprovoked seizure episodes. Posttraumatic seizure (PTS) was defined as a single, nonrecurrent convulsive episode that occurred > 24 hours following injury. Seizures within 24 hours of the injury were defined as immediate PTS.

Of 290 children eligible for this study, 191 of them or their caregivers were reached by telephone survey and were included in the analysis. Most injuries (80.6%) were due to falls. Six children had immediate PTS. All children underwent CT imaging; of them, 72.8% demonstrated fractures and 10.5% did not demonstrate acute findings. The mean follow-up was 7.4 years. Seven children (3.7%) experienced PTS; of them, 6 (85.7%) developed epilepsy and 3 (42.9%) developed intractable epilepsy. The overall incidence of epilepsy and intractable epilepsy in this cohort was 3.1% and 1.6%, respectively. None of the children who had immediate PTS developed epilepsy. Children who developed epilepsy spent an average of 2 extra days in the hospital at the time of the injury. The mean time between trauma and onset of seizures was 3.1 years. Immediate PTS was not correlated with PTE.

In this analysis of data from medical records and long-term follow-up, MTBI was found to confer increased risk for the development of PTE and intractable PTE, of 4.5 and 8 times higher, respectively. As has been established in adults, these findings confirm that MTBI increases the risk for PTE in the pediatric population 7).

2015

Park et al. performed a retrospective electronic chart review of patients who had suffered traumatic brain injury and subsequently evaluated at Children’s Hospital of Michigan from 2002 to 2012. Various epidemiologic and clinical variables were analyzed.

Patients who had severe traumatic brain injury and post-traumatic epilepsy had an abnormal acute head computed tomography. These patients had increased number of different seizure types, increased risk of intractability of epilepsy, and were on multiple antiepileptic drugs. Hypomotor seizure was the most common seizure type in these patients. There was a high prevalence of patients who suffered nonaccidental trauma, all of whom had severe traumatic brain injury.

This study demonstrates a need for biomarkers in children following traumatic brain injury to reliably evaluate the risk of post-traumatic epilepsy 8).

2013

Children ages 6-17 years with one or more risk factors for the development of posttraumatic epilepsy, including presence of intracranial hemorrhage, depressed skull fracture, penetrating injury, or occurrence of posttraumatic seizure were recruited into a phase II study. Treatment subjects received levetiracetam 55 mg/kg/day, b.i.d., for 30 days, starting within 8 h postinjury. The recruitment goal was 20 treated patients. Twenty patients who presented within 8-24 h post-TBI and otherwise met eligibility criteria were recruited for observation. Follow-up was for 2 years. Forty-five patients screened within 8 h of head injury met eligibility criteria and 20 were recruited into the treatment arm. The most common risk factor present for pediatric inclusion following TBI was an immediate seizure. Medication compliance was 95%. No patients died; 19 of 20 treatment patients were retained and one observation patient was lost to follow-up. The most common severe adverse events in treatment subjects were headache, fatigue, drowsiness, and irritability. There was no higher incidence of infection, mood changes, or behavior problems among treatment subjects compared to observation subjects. Only 1 (2.5%) of 40 subjects developed posttraumatic epilepsy (defined as seizures >7 days after trauma). This study demonstrates the feasibility of a pediatric posttraumatic epilepsy prevention study in an at-risk traumatic brain injury population. Levetiracetam was safe and well tolerated in this population. This study sets the stage for implementation of a prospective study to prevent posttraumatic epilepsy in an at-risk population 9).

1) , 6)

Keret A, Shweiki M, Bennett-Back O, Abed-Fteiha F, Matoth I, Shoshan Y, Benifla M. The clinical characteristics of posttraumatic epilepsy following moderate-to-severe traumatic brain injury in children. Seizure. 2018 Mar 20;58:29-34. doi: 10.1016/j.seizure.2018.03.018. [Epub ahead of print] PubMed PMID: 29609147.
2) , 7)

Keret A, Bennett-Back O, Rosenthal G, Gilboa T, Shweiki M, Shoshan Y, Benifla M. Posttraumatic epilepsy: long-term follow-up of children with mild traumatic brain injury. J Neurosurg Pediatr. 2017 Jul;20(1):64-70. doi: 10.3171/2017.2.PEDS16585. Epub 2017 May 5. PubMed PMID: 28474982.
3) , 8)

Park JT, Chugani HT. Post-traumatic epilepsy in children-experience from a tertiary referral center. Pediatr Neurol. 2015 Feb;52(2):174-81. doi: 10.1016/j.pediatrneurol.2014.09.013. Epub 2014 Oct 12. PubMed PMID: 25693582.
4)

Arndt DH, Goodkin HP, Giza CC. Early Posttraumatic Seizures in the Pediatric Population. J Child Neurol. 2016 Jan;31(1):46-56. doi: 10.1177/0883073814562249. Epub 2015 Jan 6. Review. PubMed PMID: 25564481.
5)

Piccenna L, Shears G, O’Brien TJ. Management of post-traumatic epilepsy: An evidence review over the last 5 years and future directions. Epilepsia Open. 2017 Mar 17;2(2):123-144. doi: 10.1002/epi4.12049. eCollection 2017 Jun. PubMed PMID: 29588942; PubMed Central PMCID: PMC5719843.
9)

Pearl PL, McCarter R, McGavin CL, Yu Y, Sandoval F, Trzcinski S, Atabaki SM, Tsuchida T, van den Anker J, He J, Klein P. Results of phase II levetiracetam trial following acute head injury in children at risk for posttraumatic epilepsy. Epilepsia. 2013 Sep;54(9):e135-7. doi: 10.1111/epi.12326. Epub 2013 Jul 22. PubMed PMID: 23876024; PubMed Central PMCID: PMC3769484.

Update: Tethered Cord Syndrome in Adulthood

Tethered Cord Syndrome in Adulthood

Symptoms related to a congenital tethered cord occur most commonly in childhood, so it was initially regarded as a pediatric problem; but in many patients, the diagnosis is not established until symptoms manifest in adulthood.

The number of adults in whom congenital TCS is diagnosed continues to grow as a result of better imaging and recognition of this syndrome. Pediatric TCS has been well studied in the literature, but much of the information regarding the adult population is still being defined. Patients who never undergo treatment for TCS likely have an elevated risk of developing symptoms with advancing age 1).

Epidemiology

Adult tethered cord syndrome is a rare neurological disorder that classically presents with back or leg pain, weakness, and urinary dysfunction. Spinal cord tethering has been associated with acquired Chiari malformations.

Evaluation

Radiographically: low conus medullaris (below L2) and thickened filum terminale. NB:apparent filum terminale diameter on CT myelogram may vary with concentration of contrast material.

Preoperative cystometrogram is strongly recommended, especially if the patient seems continent (postoperative changes in bladder function are not uncommon, possibly due to stretching of the lower fibers of the cauda equina).

Differential diagnosis

It is difficult to differentiate a tethered cord from a congenitally low lying conus (filum diameter is generally normal in the latter).

Treatment

Standard treatment for TCS diagnosed in adulthood remains controversial. Surgical intervention is usually indicated based on an expected natural history of disease progression in the absence of treatment.

Some adults with TCS decline surgery despite severe neurologic deficit 2).

Surgical treatment

If the only abnormality is a thickened, shortened filum terminale, then a limited lumbosacral laminectomy may suffice, with division of the filum once identified.

If a lipoma is found, it may be removed with the filum if it separates easily from neural tissues.

The filum is differentiated from nerve roots by presence of characteritics squiggly vessel on surface of filum. Also, under the microscope, the filum has a distinctively whiter appearance than the nerve roots, and ligamentous-like strands can be seen running through it. NB: intra-op electrical stimulation and recording of anal sphincter EMG are more definitive.

Technique

In the series of Gao et al. all patients received general anesthesia and took their prone position, neural electrophysiological monitoring electrode were then placed, followed by the acquisition and collection of muscle electromyography signals from the anal sphincter, bilateral musculus vastus lateralis, gastrocnemius and mesothenar. A total of 72 cases applied positive straight incision, 10 cases of lumbosacral lipoma with longitudinal incision. After exposing the dura mater spinalis, it was cut from the normal anatomical structure to the lesion. Cauda equina was managed by sharp releasing adhesion under the nerve electrophysiological monitoring, tumors were removed with the use of medical ultrasonic dissector. After the tumor was removed, the dura mater spinalis with low tonus was closed by water, and the dura mater spinalis with high tonus was formed by the autogenous fascia. For patients combined with subcutaneous giant lipoma in the lumbosacral region, the subcutaneous tumor was removed, and the drainage tube was placed into the left empty cavity, followed by pressurized dressing and vacuum aspiration 3).

Outcome

Surgical release is usually good for pain relief. However, it is poor for return of bladder function.

Results of clinical studies of surgical intervention in adulthood are encouraging 4)5) 6).

It is safe and effective for improving pain and neurological status in the majority of patients; however, patients who have undergone previous intradural detethering procedures in general fare less well, and considerable judgment is required in their management 7).

In a multivariate regression model, laminectomy, bladder dysfunction when associated to muscular weakness, and long-term (>6 months) symptoms were selected as the independent risk factors associated with poor or minimally improved (almost unchanged) surgical outcomes. When the urodynamic test showed overactive detrusor muscle, no improvement was recorded in postoperative urodynamic test. Laminoplasty (or hemilaminectomy), short-term (<6 months) symptoms, patients without lipomas, and presentation with moderate or mild symptoms seem to be proper predictors for good surgical outcomes. Further prospective studies are necessary to investigate these findings systematically. Urodynamic study can be used as a predictive tool for close follow-up of asymptomatic adult patients involved with TCS 8).

Case reports

A 68-year-old man with a history of distant T12-level spinal cord injury who presented with two weeks of progressive bilateral lower extremity weakness. The patient underwent a T12-L1 laminectomy in 1977, complicated by arachnoiditis and syringomyelia, with eventual placement of a syringo-pleural shunt. He remained neurologically stable until 2012, when he underwent a suboccipital craniectomy for Chiari decompression for new-onset headache and dysphagia. Ten days later, the patient noted progressive leg weakness and radiographic evidence of spinal cord tethering at the T11-T12 level. A T10-L1 laminectomy and medical facetectomy was undertaken for detethering with postoperative recovery of ambulatory function with assistance.

The patient presented with an unusual acquisition of tethered cord syndrome. The tethering of the spinal cord may have been triggered by arachnoid adhesions from initial lumbar surgery 35 years prior to presentation and subsequently exacerbated by alterations of CSF dynamics following Chiari decompression. Given the potentially devastating sequelae of tethered cord syndrome, investigation of CSF flow dynamics may be beneficial prior to operative intervention in patients with risk factors for a tethered cord who present with adult-onset Chiari malformation 9).

1) , 4)

Rajpal S, Tubbs RS, George T, Oakes WJ, Fuchs HE, Hadley MN, Iskandar BJ. Tethered cord due to spina bifida occulta presenting in adulthood: a tricenter review of 61 patients. J Neurosurg Spine. 2007 Mar;6(3):210-5. PubMed PMID: 17355019.
2)

Düz B, Gocmen S, Secer HI, Basal S, Gönül E. Tethered cord syndrome in adulthood. J Spinal Cord Med. 2008;31(3):272-8. PubMed PMID: 18795476; PubMed Central PMCID: PMC2565560.
3)

Gao J, Kong X, Li Z, Wang T, Li Y. Surgical treatments on adult tethered cord syndrome: A retrospective study. Medicine (Baltimore). 2016 Nov;95(46):e5454. PubMed PMID: 27861396; PubMed Central PMCID: PMC5120953.
5) , 7)

Lee GY, Paradiso G, Tator CH, Gentili F, Massicotte EM, Fehlings MG. Surgical management of tethered cord syndrome in adults: indications, techniques, and long-term outcomes in 60 patients. J Neurosurg Spine. 2006 Feb;4(2):123-31. PubMed PMID: 16506479.
6)

van Leeuwen R, Notermans NC, Vandertop WP. Surgery in adults with tethered cord syndrome: outcome study with independent clinical review. J Neurosurg. 2001 Apr;94(2 Suppl):205-9. PubMed PMID: 11302621.
8)

Abdallah A, Emel E, Abdallah BG, Asiltürk M, Sofuoğlu ÖE. Factors affecting the surgical outcomes of tethered cord syndrome in adults: a retrospective study. Neurosurg Rev. 2018 Jan;41(1):229-239. doi: 10.1007/s10143-017-0842-z. Epub 2017 Mar 14. PubMed PMID: 28293750.
9)

Jackson C, Yang BW, Bi WL, Chiocca EA, Groff MW. Adult tethered cord syndrome following Chiari decompression. World Neurosurg. 2018 Jan 31. pii: S1878-8750(18)30208-0. doi: 10.1016/j.wneu.2018.01.165. [Epub ahead of print] PubMed PMID: 29409774.

XXXIV Reunión de la Sociedad Española de Neurocirugía Pediátrica

Este año la XXXIV Reunión de la Sociedad Española de Neurocirugía Pediátrica la celebraremos en Donostia-San Sebastián del 22 al 24 de Febrero

Programa


9:00 h – 11:00 h PATOLOGÍA ONCOLÓGICA

Tumores pediátricos en niños menores de tres años. PROF. EDGARDO SPAGNUOLO.
Jefe Servicio Neurocirugía Hospital Maciel Unidad Docente,
Escuela de Graduados. Uruguay.

Medulloblastoma. PROF. MAURICE CHOUX. Hôpital des Enfants, La Timone. Francia.

Patología de la región selar y paraselar en la infancia. DR. AMETS SAGARRIBAY IRAÑETA.
Servicio de Neurocirugía. Centro Hospitalar de Lisboa Central. Portugal.

Cranial, spinal and peripheral nerve affection in children with Neurofibromatosis-an Overview. DR. MARCUS TATAGIBA. Departamento de Neurocirugía, Hospital Universitario
de Tubingen, Alemania

Brainstem Tumors in Children. PROF. MAURICE CHOUX.
Hôpital des Enfants, La Timone. Francia.

Gliomas difusos de protuberancia: estado actual y presentación de un ensayo clínico.
DRA. SONIA TEJADA SOLÍS. Servicio de Neurocirugía.
Clínica Universidad de Navarra.
Pamplona, España.

Importancia de la caracterización molecular en meduloblastomas.
DRA. IDOIA GARCÍA CAMINO. Unidad de Investigación de Cáncer
Infantil del Grupo de Oncología Celular del Instituto Biodonostia.
San Sebastián, España.

Actualización en la clasificación y gradación de los tumores del SNC. El consenso de Haarlem.
DRA. IRUNE RUIZ DÍAZ. Jefe de Servicio de Anatomía Patológica.
Hospital Universitario Donostia. San Sebastián, España.

Ependimoma. Ensayo SIOP-Ependymoma II. Revisión centralizada.
DRA. ANA FERNÁNDEZ-TEIJEIRO ÁLVAREZ. Jefe de Sección de la Unidad de Onco-Hematología Pediátrica Hospital Universitario Virgen Macarena. Sevilla, España.

Aportación de ultrasonidos en Neurocirugía”. DR. CRISTIAN DE QUINTANA.
Servicio de Neurocirugía. Hospital de la Santa Creu i Sant Pau. Barcelona, España.

“Aportación de la neuronavegación en Neurocirugía Pediátrica”.
DR. JAVIER SACEDA GUTIÉRREZ.
Servicio de Neurocirugía, Hospital Universitario La Paz. Madrid, España.

Encephaloclastic cyst

Poorly circumscribed areas of parenchymal destruction associated with cystic components.

Encephaloclastic cysts provoked by intraventricular chemotherapy are very uncommon.

Rare complication of a malfunctioning methotrexate Ommaya reservoir 1) 2).

Pathogenesis

The pathogenesis may result from alterations in CSF pulsations with retrograde flow of intraventricular chemotherapy into the brain parenchyma and subsequent development of a local chemical encephalopathy.

Mella et al. report two rare cases of encephaloclastic cyst with intraventricular topotecan use. The patients were diagnosed and treated at The University of Texas MD Anderson Cancer Center. They consented to the publication of their laboratory results and imaging studies for educational purposes.

The patients presented with metastatic cancers (breast/lung) complicated by leptomeningeal disease. Ommaya reservoirs were placed in both cases and patients were initiated on intraventricular topotecan at 0.4 mg twice weekly. After approximately 12 intraventricular treatments, both patients developed confusion, seizures and headaches. MRI of the brain demonstrated cystic dilatation of the brain parenchyma around the catheter that connects to the reservoir dome and delivers the drug to the intraventricular space. The catheter was surrounded by vasogenic edema. Catheters were removed and analyzed and were found to be intact. CSF analyses showed no evidence of infection or malignancy. Intraventricular topotecan was discontinued and both patients demonstrated sustained clinical and radiological responses.

These cases highlight an atypical complication of intraventricular use of topotecan with successful management 3).

1)

Chowdhary S, Chalmers LM, Chamberlain PA. Methotrexate-induced encephaloclastic cyst: a complication of intraventricular chemotherapy. Neurology. 2006 Jul 25;67(2):319. PubMed PMID: 16864827.
2)

Lubomski M, Pell M, Lochhead A, Jude M. Encephaloclastic cyst: a rare complication of a malfunctioning methotrexate Ommaya reservoir. Intern Med J. 2018 Feb;48(2):224-226. doi: 10.1111/imj.13704. PubMed PMID: 29415363.
3)

Mella DB, Kamiya-Matsuoka C, Liao B, Tummala S, de Groot J. Recurrent encephaloclastic cyst induced by intraventricular topotecan. J Neurol Sci. 2015 Feb 15;349(1-2):52-3. doi: 10.1016/j.jns.2014.12.024. Epub 2014 Dec 24. PubMed PMID: 25598491.

Update: Cerebellopontine angle pilocytic astrocytoma

Cerebellopontine angle pilocytic astrocytoma

A rare case of a 55-yr old patient of pilocytic astrocytoma of the cerebellopontine angle mimicking a vestibular schwannoma. The tumor protruded into the porus acusticus causing enlargement of the internal auditory meatus, which is quite an unusual feature of glial tumor 1).


Schneider et al. report a pilocytic astrocytoma of the cerebellopontine angle in a child presenting with auditory neuropathy spectrum disorder 2).


Mirone et al. describe a rare case of pediatric pilocytic astrocytoma presented as a right cerebellopontine angle (CPA) mass, completely separated from the brainstem and arising from the proximal VIII cranial nerve portion.

A 12-year-old boy, with no evidence of neurofibromatosis type 2, presented with progressive hearing loss at the right ear and headache. An initial enhanced magnetic resonance examination suggested the diagnosis of schwannoma. The tumor was resected by a suboccipital retrosigmoid approach.

The case seems to be the first report of a primary pediatric CPA pylocitic astrocytoma arising from the VIII nerve complex and presenting internal auditory canal enlargement. It represents the third reported case of a primary CPA pilocytic astrocytoma (the second pediatric case with the first arising from V nerve) and the eighth report of primary CPA glioma, overall 3).


A case of pilocytic astrocytoma of the cerebellum mimicking an acoustic schwannoma. The tumour protruded into the porus acusticus and enlarged the internal auditory meatus, which is a quite unusual characteristic of glial tumours 4).

1)

Dutta G, Singh D, Singh H, Sachdeva D, Kumar V, Chaturvedi A. Pilocytic astrocytoma of the cerebellopontine angle mimicking vestibular schwannoma: report of a rare entity. Br J Neurosurg. 2017 Dec 26:1-3. doi: 10.1080/02688697.2017.1419163. [Epub ahead of print] PubMed PMID: 29278012.
2)

Schneider F, Kompis M, Ozdoba C, Beck J, Caversaccio M, Senn P. Pilocytic astrocytoma of the cerebellopontine angle in a child presenting with auditory neuropathy spectrum disorder. Otol Neurotol. 2015 Apr;36(4):e101-3. doi: 10.1097/MAO.0000000000000355. PubMed PMID: 24781101.
3)

Mirone G, Schiabello L, Chibbaro S, Bouazza S, George B. Pediatric primary pilocytic astrocytoma of the cerebellopontine angle: a case report. Childs Nerv Syst. 2009 Feb;25(2):247-51. doi: 10.1007/s00381-008-0690-9. Epub 2008 Aug 9. PubMed PMID: 18690462.
4)

Takada Y, Ohno K, Tamaki M, Hirakawa K. Cerebellopontine angle pilocytic astrocytoma mimicking acoustic schwannoma. Neuroradiology. 1999 Dec;41(12):949-50. PubMed PMID: 10639675.