Andrew B. Foy

Photodynamic therapy (PDT) for malignant brain tumors — Where do we stand?

INTRODUCTION What is the current status of photodynamic therapy (PDT) with regard to treating malignant brain tumors? Despite several decades of effort, PDT has yet to achieve standard of care. PURPOSE The questions we wish to answer are: where are we clinically with PDT, why is it not standard of care, and what is being done in clinical trials to get us there. METHOD Rather than a meta-analysis or comprehensive review, our review focuses on who the major research groups are, what their approaches to the problem are, and how their results compare to standard of care. Secondary questions include what the effective depth of light penetration is, and how deep can we expect to kill tumor cells. CURRENT RESULTS A measurable degree of necrosis is seen to a depth of about 5mm. Cavitary PDT with hematoporphyrin derivative (HpD) results are encouraging, but need an adequate Phase III trial. Talaporfin with cavitary light application appears promising, although only a small case series has been reported. Foscan for fluorescence guided resection (FGR) plus intraoperative cavitary PDT results were improved over controls, but are poor compared to other groups. 5-Aminolevulinic acid-FGR plus postop cavitary HpD PDT show improvement over controls, but the comparison to standard of care is still poor. CONCLUSION Continued research in PDT will determine whether the advances shown will mitigate morbidity and mortality, but certainly the potential for this modality to revolutionize the treatment of brain tumors remains. The various uses for PDT in clinical practice should be pursued.

Stereotactic Radiosurgery for Pediatric Arteriovenous Malformations

Children with intracranial arteriovenous malformations (AVM) have a high cumulative risk of hemorrhage and therefore effective treatment of AVMs in the pediatric population is imperative. Treatment options include microsurgical resection, endovascular embolization, staged or single fraction radiosurgery, or some combination of these treatments, with the ultimate goal of eliminating the risk of hemorrhage. In this article the authors review the current data on the use of radiosurgery for the treatment of childhood AVMs. Factors associated with successful AVM radiosurgery in this population are examined, and comparisons with outcomes in adult patients are reviewed.

Histologic analysis of a human trigeminal nerve after failed stereotactic radiosurgery: case report

BACKGROUND Stereotactic radiosurgery is an accepted surgery to treat patients with medically intractable trigeminal neuralgia. However, little is known about the mechanism of pain relief after trigeminal neuralgia radiosurgery. We report the histologic findings of a human trigeminal nerve after failed radiosurgery for trigeminal neuralgia. CASE DESCRIPTION A 74-year-old patient presented with a 10-year history of refractory trigeminal neuralgia. Prior surgeries included an MVD and PRGR. Gamma knife radiosurgery was performed targeting the proximal trigeminal nerve using one 4-mm isocenter (maximum dose, 85 Gy). She experienced good pain relief (no pain, reduced medications) for 16 months. She had no new trigeminal deficits after this procedure. The pain recurred, and she underwent repeat gamma knife radiosurgery targeting the distal trigeminal nerve using one 4-mm isocenter (maximum dose, 70 Gy). The pain continued to escalate until she required hospitalization for pain control and hydration. Three weeks after her second radiosurgical procedure, she underwent a repeat posterior fossa exploration. During that surgery, her trigeminal nerve was partially sectioned, and a small segment of the proximal to midcisternal nerve was sent for histological examination. There was no histologic evidence of nerve damage. CONCLUSION This case supports the contention that trigeminal nerve injury is required to provide long lasting pain relief after trigeminal neuralgia radiosurgery.

Intracranial subdural empyema after surgery for lumbar lipomyelomeningocele: A rare complication

Background: Surgery is routinely recommended for lumbar lipomyelomeningocele, especially in the setting of tethered cord syndrome. The most common complications are wound infections and cerebrospinal fluid (CSF) leak, which remain confined to the surgical site. To the best of our knowledge, there have been no prior reports relating an intracranial subdural empyema following detethering surgery. Prompt diagnosis is essential since subdural empyema is a neurosurgical emergency. Case Description: The patient was an 11-month-old male who underwent detethering surgery for a lumbar lipomyelomeningocele. This was followed by wound drainage consistent with CSF leak, requiring revision. Cultures grew three aerobes (Escherichia coli, Enterococcus, and Klebsiella) and three anaerobes (Clostridium, Veillonella, and Bacteroides). He was started on cefepime, vancomycin, and flagyl. The patient required two more wound revisions and placement of an external ventricular drain (EVD) secondary to persistent wound leakage. A subsequent magnetic resonance imaging (MRI) brain was carried out due to protracted irritability, which revealed extensive left subdural empyema along the parietooccipital region and the inferior and anterior temporal lobe. He underwent evacuation of the subdural empyema where cultures exhibited no growth. Subsequently, he progressed well. His lumbar incision continued to heal. Serial MRI brains and inflammatory markers were reassuring. He weaned off his EVD and went home to complete a 6-week course of antibiotics. Upon completion of his antibiotics, he returned for a clinic visit; he exhibited no interim fevers or wound issues; cranial imaging documented no evidence of a residual or recurrent subdural empyema. Conclusion: Intracranial subdural empyema may occur after wound complications from detethering surgery despite early initiation of broad-spectrum antibiotics. Possible etiology may be local wound infection that seeds the subdural space and travels to the cranium, leading to meningitis and subdural empyema. Such a scenario should prompt surveillance imaging of the head as undiagnosed subdural empyema may lead to devastating consequences.

Penetrating head injuries in children due to BB and pellet guns: a poorly recognized public health risk

OBJECT Nonpowder guns, defined as spring- or gas-powered BB or pellet guns, can be dangerous weapons that are often marketed to children. In recent decades, advances in compressed-gas technology have led to a significant increase in the power and muzzle velocity of these weapons. The risk of intracranial injury in children due to nonpowder weapons is poorly documented. METHODS A retrospective review was conducted at 3 institutions studying children 16 years or younger who had intracranial injuries secondary to nonpowder guns. RESULTS The authors reviewed 14 cases of intracranial injury in children from 3 institutions. Eleven (79%) of the 14 children were injured by BB guns, while 3 (21%) were injured by pellet guns. In 10 (71%) children, the injury was accidental. There was 1 recognized assault, but there were no suicide attempts; in the remaining 3 patients, the intention was indeterminate. There were no mortalities among the patients in this series. Ten (71%) of the children required operative intervention, and 6 (43%) were left with permanent neurological injuries, including epilepsy, cognitive deficits, hydrocephalus, diplopia, visual field cut, and blindness. CONCLUSIONS Nonpowder guns are weapons with the ability to penetrate a childs skull and brain. Awareness should be raised among parents, children, and policy makers as to the risk posed by these weapons.

Prone positioning for successful gamma knife radiosurgical treatment of far anterior skull base lesions: a technical note.

BACKGROUND Gamma Knife targeting is geometrically limited by the physical dimensions of the head, helmet, headframe, and the radiation target position. All four aspects need to be considered for accurate treatment planning. Within the available space, delivery of the treatment isodose is based on the target position, which must be brought into the center of the collimator. In cases of anatomically challenging target positions in far eccentric locations of the head, careful treatment planning needs to be performed that does not exceed the limits of the system. CLINICAL PRESENTATION We describe a case of a challenging far anterior ethmoid sinus hemangiopericytoma in an 80-year-old woman. TECHNIQUE The tumor was treated successfully by positioning the patient prone on a Model C Gamma unit. The physical restrictions of the Gamma Knife surgical system and the rationale for improved anterior targeting using the prone position are discussed. CONCLUSION A thoughtful approach to positioning in challenging anterior lesions extends the targeting capabilities of certain Gamma units.

Management and outcomes of pediatric vocal cord paresis in Chiari malformation

INTRODUCTION Pediatric vocal cord paresis (VCP) has a variety of etiologies, including congenital neurologic disease. Arnold-Chiari Malformation (ACM) is one such disease with known VCP association. However, the natural history, need for tracheostomy, and rate of decannulation in this patient population is not well characterized. OBJECTIVE To provide prognostic information on infants with ACM and VCP. METHODS A retrospective chart review was conducted of patients with both ACM and VCP at a single institution. Clinical outcomes and disease progression were determined using flexible laryngoscopy, serial clinical exams, and operative reports from otolaryngology and neurosurgery services. RESULTS Eighteen patients were included in this study, four with ACM Type I and 14 with ACM Type II. These groups were analyzed separately. For ACM I, the average age at diagnosis was 25 months and two (50%) required tracheostomy. Three subjects (75%) achieved VCP resolution, with two doing so after neurosurgical decompression. For ACM II, the average age at diagnosis was eight months and 12 patients (86%) underwent tracheostomy. Four subjects with tracheostomy (33%) achieved decannulation, with three of these demonstrating VCP resolution. In total, six ACM II patients had complete and one had partial VCP resolution, all of whom underwent decompression. Two patients initially had normal endoscopic exams despite stridor and VCP was only noted on serial exams. DISCUSSION This study represents the largest series of pediatric patients with VCP and ACM. The majority needed decompression (80%) and tracheotomy (78%). Tracheostomy decannulation typically occurred only after decompression and resolution of VCP. No children diagnosed at age <1 month were decannulated. Early decompression was associated with successful avoidance of tracheostomy in majority of Chiari I but not Chiari II patients. Serial endoscopies were required to confirm VCP in some patients. This information could potentially aid in management and counseling parents of children with VCP and CM.

En bloc resection of a C-1 lateral mass osteosarcoma: technical note

Osteosarcoma is an aggressive primary bone tumor. It is currently treated with multimodality therapy including en bloc resection, which has been demonstrated to confer a survival benefit over intralesional resection. The authors present the case of an 8-year-old girl with a C-1 lateral mass osteosarcoma, which was treated with a 4-stage en bloc resection and spinal reconstruction. While technically complex, the feasibility of en bloc resection for spinal osteosarcoma should be explored in the pediatric population.