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Brian J. Dlouhy and Arnold H. Menezes

Osteopetrosis is a heterogeneous group of rare, inherited disorders of the skeleton that results in neurological manifestations due to restriction of growth of cranial foramina and calvarial thickening. A 25-year-old woman with a history of autosomal dominant osteopetrosis presented to the authors' institution with headache worsened by exertion and radiating from the occipital region forward with episodes of choking/coughing when eating and a loss of gag reflex on physical examination. On MR imaging, she was found to have severe posterior fossa calvarial thickening resulting in a small posterior fossa and tonsillar ectopia of 9 mm and compression and deformation of the brainstem. She underwent posterior fossa craniectomy, foramen magnum decompression, and partial C-1 laminectomy with external durotomy. The patient did well postoperatively with resolution of symptoms. This case describes a new neurological manifestation of autosomal dominant osteopetrosis. To the authors' knowledge, this report represents the first described case of extreme posterior fossa calvarial thickening from autosomal dominant osteopetrosis with associated Chiari I malformation (CM-I) requiring posterior fossa decompression and extradural decompression. Given previously published MR imaging data that demonstrate the association of osteopetrosis and CM may be more common than in this case alone, the authors discuss the need for further investigation of the incidence of CM-I in patients with autosomal dominant osteopetrosis. Additionally, they review osteopetrosis and other diagnoses of calvarial hyperostosis presenting as CM-I.

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Brian J. Dlouhy and Arnold H. Menezes

OBJECT

Techniques for combined extradural and intradural decompression with expansile duraplasty for Chiari malformation type I (CM-I) have been well described, with various allogenic and autologous materials used for duraplasty. However, the approach and surgical technique used for duraplasty in our treatment of CM-I and developed by the senior author in the 1990s has not been described.

METHODS

A prospective database was initiated in March 2003 to denote the use of cervical fascia for duraplasty and incorporate an ongoing detailed record of complications during the surgical treatment of children and adults with CM-I with and without syringomyelia. A total of 389 surgeries for CM-I were performed on 379 patients from March 2003 to June 2016. A total of 123 posterior procedures were performed on 123 patients in which both a posterior fossa extradural and intradural decompression with duraplasty (extra-intradural) was performed. In this paper the authors describe the surgical technique for harvesting and using cervical fascia for duraplasty in the surgical treatment of CM-I and analyze and discuss complications from a prospective database spanning 2003–2016.

RESULTS

The authors found that cervical fascia can be harvested in patients of all ages (2–61 years old) without difficulty, and it provides a good substitute for dura in creating an expansile duraplasty in patients with CM-I. Cervical fascia is an elastic-like material with a consistency that allows for a strong watertight closure. Harvesting the cervical fascia graft does not require any further extension of the incision superiorly or inferiorly to obtain the graft. Complications were uncommon in this study of 123 children and adults. The risk of any type of complication (aseptic meningitis, CSF leak, pseudomeningocele, infection, development of hydrocephalus, and need for ventriculoperitoneal shunt) for the 78 patients in the pediatric age group was 0%. The risk of complication in the adult group was 6.7% (1 patient with aseptic meningitis and 2 patients with CSF leak).

CONCLUSIONS

Autologous cervical fascia is easy to obtain in patients of all ages and provides an effective material for duraplasty in the treatment of CM-I. Complications from the combination of both an extradural and intradural decompression with autologous cervical fascia duraplasty are uncommon.

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Brian J. Dlouhy, Nader S. Dahdaleh, Arnold H. Menezes and MD

The craniovertebral junction (CVJ), or the craniocervical junction (CCJ) as it is otherwise known, houses the crossroads of the CNS and is composed of the occipital bone that surrounds the foramen magnum, the atlas vertebrae, the axis vertebrae, and their associated ligaments and musculature. The musculoskeletal organization of the CVJ is unique and complex, resulting in a wide range of congenital, developmental, and acquired pathology. The refinements of the transoral approach to the CVJ by the senior author (A.H.M.) in the late 1970s revolutionized the treatment of CVJ pathology. At the same time, a physiological approach to CVJ management was adopted at the University of Iowa Hospitals and Clinics in 1977 based on the stability and motion dynamics of the CVJ and the site of encroachment, incorporating the transoral approach for irreducible ventral CVJ pathology. Since then, approaches and techniques to treat ventral CVJ lesions have evolved. In the last 40 years at University of Iowa Hospitals and Clinics, multiple approaches to the CVJ have evolved and a better understanding of CVJ pathology has been established. In addition, new reduction strategies that have diminished the need to perform ventral decompressive approaches have been developed and implemented.

In this era of surgical subspecialization, to properly treat complex CVJ pathology, the CVJ specialist must be trained in skull base transoral and endoscopic endonasal approaches, pediatric and adult CVJ spine surgery, and must understand and be able to treat the complex CSF dynamics present in CVJ pathology to provide the appropriate, optimal, and tailored treatment strategy for each individual patient, both child and adult. This is a comprehensive review of the history and evolution of the transoral approaches, extended transoral approaches, endoscopie assisted transoral approaches, endoscopie endonasal approaches, and CVJ reduction strategies. Incorporating these advancements, the authors update the initial algorithm for the treatment of CVJ abnormalities first published in 1980 by the senior author.

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Brian J. Dlouhy, Michael P. Chae and Charles Teo

OBJECT

The supraorbital eyebrow approach utilizes an eyebrow skin incision to fashion a supraorbital craniotomy for exposure of the subfrontal corridor. This provides anterolateral access to surgical lesions in the anterior cranial fossa, parasellar regions, brainstem, and medial temporal lobe. With use of the endoscope, further areas can be accessed. This approach has been applied effectively in adults, but questions remain about its use in children—specifically with regard to adequate working space, effectiveness for achieving the desired results, cosmesis, and complications.

METHODS

The authors conducted a retrospective review of more than 450 cases involving patients of all ages who had undergone a supraorbital eyebrow approach performed by the senior author (C.T.) from 1995 to 2013. Only cases involving patients younger than 18 years with a minimum follow-up of 6 weeks were included in this study. All inpatient and outpatient records were retrospectively reviewed and clinical/operative outcomes, cosmetic results, and complications were recorded. In the present article, the authors briefly describe the surgical approach and highlight any differences in applying it in children.

RESULTS

Fifty-four pediatric patients who had undergone a supraorbital eyebrow approach met inclusion criteria. The pathological conditions consisted mostly of tumors or other resectable lesions. In a total of 51 resectable lesions, 44 surgeries resulted in a gross-total (100%) resection and 7 cases resulted in subtotal (50%–99%) resection. The endoscope assisted and expanded visualization or provided access to areas not reached by standard microscopic visualization in all cases. Cosmetic outcomes were excellent. In all cases, the incisional scar was barely visible at 6 weeks. In 3 cases a minor bone defect was observed on the forehead. Given the small size of the frontal sinus in children, no frontal sinus breaches occurred. Additionally, no CSF leak or wound infection was identified.

CONCLUSIONS

The supraorbital eyebrow approach is extremely effective in achieving desired results in properly selected cases in patients of all pediatric age ranges, from infants to teenagers. There is sufficient working space for the endoscope and all instruments, allowing for endoscopic assistance and bimanual surgical technique. Cosmetic results are excellent, and complications related to the approach are minimal.

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Nader S. Dahdaleh, Brian J. Dlouhy and Arnold H. Menezes

Object

The treatment of basilar invagination in the pediatric age group is dependent on the possibility of preoperative reduction. Reducible lesions obviate a ventral decompression and require a dorsal-only approach for stabilization with or without a suboccipital decompression.

Methods

The authors describe a technique of intraoperative reduction of basilar invagination with the use of general anesthesia and neuromuscular blockade in the presence of crown halo traction. Using the O-arm device, a 3D CT scan is generated in the sagittal plane to demonstrate the reduction intraoperatively. This technique was successful in 6 pediatric patients with basilar invagination.

Results

The average age of the patients was 10.8 years, and they were followed for a mean period of 8.5 months. The patients had mild basilar invagination or partial reduction in extension on preoperative MR imaging. Intraoperative reduction was demonstrated in all patients by using the reported technique with intraoperative CT. All patients underwent occipitocervical fusion, and all but one underwent a suboccipital decompression. There were no complications related to the operation, and all but one reported improvement of symptoms on the last postoperative visit.

Conclusions

Intraoperative reduction performed using neuromuscular blockade and intraoperative traction is an effective method for further reduction of basilar invagination in the pediatric age group. This is the first reported application of intraoperative CT imaging performed using the O-arm device in craniocervical surgery in which successful reduction is demonstrated in detail.

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Brian J. Dlouhy, Jeffrey D. Dawson and Arnold H. Menezes

OBJECTIVE

The pathophysiology underlying tonsillar herniation and CSF obstruction in Chiari malformation Type I (CM-I) is unclear, and the cause of CM-I–associated syringomyelia is not well understood. A better understanding of this pathophysiology is important for an improved treatment strategy. Therefore, the authors sought to identify, characterize, and examine the intradural pathology and CSF flow pathophysiology in the posterior fossa and at the level of the foramen magnum that occurs in the setting of CM-I. They determined the incidence of these intradural findings and assessed differences across age, with the degree of tonsillar herniation, and in the presence and absence of syringomyelia.

METHODS

A prospective database initiated in March 2003 recorded all intraoperative findings during surgical treatment of children and adults with CM-I with or without syringomyelia. A total of 389 surgeries for CM-I were performed in 379 patients between March 2003 and June 2016. A total of 109 surgeries were performed in 109 patients with CM-I (without osseoligamentous abnormalities) in whom both a posterior fossa extradural and intradural decompression with duraplasty was performed (first-time intradural procedures). Using a surgical microscope, intradural pathology and obstruction of CSF channels were identified and assessed. Student t-tests and Fisher’s exact tests compared groups in a series of univariate analyses, followed by multivariate logistic regression.

RESULTS

The following intradural pathological entities were observed (prevalence noted in parentheses). These include those that did not obstruct CSF flow channels: opacified arachnoid (33.0%), thickened arachnoid (3.7%), ischemic and gliotic tonsils (40.4%), tonsillar cysts (0.9%), and inferior descent of the fourth ventricle and cervicomedullary junction (CMJ) (78.0%). The following intradural pathological entities were observed to obstruct CSF flow channels: medialized tonsils (100%), tonsil overlying and obstructing the foramen of Magendie (21.1%), intertonsillar and tonsil to CMJ arachnoid adhesions (85.3%), vermian posterior inferior cerebellar artery branches obstructing the foramen of Magendie (43.1%), and arachnoid veils or webs obstructing or occluding the foramen of Magendie (52.3%). Arachnoid veils varied in type and were observed in 59.5% of patients with CM-I who had syringomyelia, which was significantly greater than the 33.3% of patients with CM-I without syringomyelia who had an arachnoid veil (p = 0.018). The presence of CM-I with an arachnoid veil had 3.22 times the odds (p = 0.013, 95% CI 1.29–8.07, by multivariate logistic regression) of being associated with syringomyelia, adjusting for tonsillar herniation. The inferior descent of the fourth ventricle and CMJ occurred with a greater degree of tonsillar herniation (p < 0.001) and correlated with a cervicomedullary kink or buckle on preoperative MRI.

CONCLUSIONS

Intradural pathology associated with CM-I with or without syringomyelia exists in many forms, is more prevalent than previously recognized in patients of all ages, and may play a role in the pathophysiology of CM-I tonsillar herniation. Arachnoid veils appear to partially obstruct CSF flow, are significantly more prevalent in cases of CM-I with syringomyelia, and therefore may play a role in the pathophysiology of CM-I–associated syringomyelia.

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Brian J. Dlouhy, Nader S. Dahdaleh and Jeremy D. W. Greenlee

Improvement in fiber optics and imaging paved the way for tremendous advancements in neuroendoscopy. These advancements have led to increasingly widespread use of the endoscope in neurosurgical procedures, which in turn incited a technological revolution leading to new approaches, instruments, techniques, and a diverse armamentarium for the treatment of a variety of neurosurgical disorders. Soft-tissue removal is often a rate-limiting aspect to endoscopic procedures, especially when the soft tissue is dense or fibrous. The authors review a series of cases involving patients treated between August 2009 and October 2010 with a new device (the NICO Myriad), a non–heat-generating, oscillating, cutting, and tissue removal instrument that can be used through the working channel of the endoscope as well as in open neurosurgical procedures. They used this device in 14 purely endoscopic intracranial procedures and 1 endoscope-assisted keyhole craniotomy. They report that the device was easy to use and found that tissue resection was more efficient than with other available endoscopic instruments, especially in the resection of fibrotic tissue. There were no observed device-related complications. The authors discuss the technical aspects of using this device in endoscopic resection of pituitary tumors, craniopharyngiomas, and colloid cysts. They also demonstrate its use in hydrocephalus and intraventricular clot removal and discuss its potential use in other neurosurgical disorders.

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Timothy W. Vogel, Brian J. Dlouhy and Matthew A. Howard III

Object

The object of this study was to evaluate the causes of plunging events associated with automatic-releasing cranial perforators at the authors' institution.

Methods

The authors analyzed a consecutive series of 1652 cranial procedures involving one type of automaticreleasing cranial perforator over a 2-year period. Plunging occurrences were recorded for 2 drill speeds: 1000 rpm in the 1st year and 800 rpm during the 2nd year. Intraoperative observations, neuroimaging studies, and clinical data were evaluated for each plunging event.

Results

The authors identified 9 plunging events for an overall incidence of 0.54%. In the 1st year, they identified 2 plunging events at a speed of 1000 rpm for an incidence of 0.19%. In an effort to reduce this occurrence, the speed of the drill was lowered to 800 rpm. There were 7 additional events, for a significantly increased incidence of 1.16% (p = 0.014, Fisher exact test) after the change was implemented. These cases spanned a number of procedures in adults and pediatric patients, including ventriculostomy placement, craniotomies for tumor resection, tumor biopsy, and endoscopic third ventriculostomy. Despite plunging, no immediate postoperative complications were noted on clinical examination.

Conclusions

While technology continues to improve cranial perforator performance, the use of such a device is still associated with a risk of complications causing dural lacerations and injury to the underlying cortex. Decreasing the drill speed may not decrease the incidence of plunging.

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Brian J. Dlouhy, Bruno A. Policeni and Arnold H. Menezes

OBJECTIVE

Os odontoideum (OO) is a craniovertebral junction (CVJ) abnormality in which an ossicle (small bone) is cranial to a hypoplastic dens by a variable gap. This abnormality can result in instability, which may be reducible or irreducible. What leads to irreducibility in OO is unclear. Therefore, the authors sought to better understand the causes of irreducibility in OO.

METHODS

A retrospective review was conducted, which identified more than 200 patients who had undergone surgical treatment for OO between 1978 and 2015 at the University of Iowa Hospitals and Clinics. Only the 41 patients who had irreducible OO were included in this study. All inpatient and outpatient records were retrospectively reviewed, and patient demographics, clinical presentation, radiographic findings, surgical treatment, and operative findings were recorded and analyzed.

RESULTS

The cohort of 41 patients who were found to have irreducible OO included both children and adults. A majority of patients were adults (61% were 18 years or older). Clinical presentation included neck pain and headache in the majority of patients (93%). Weakness, sensory disturbances, and myelopathy were invariably present in all 41 patients (100%). Down syndrome was much more common in the pediatric cohort than in the adult cohort; of the 16 pediatric patients, 6 had Down syndrome (38%), and none of the adults did. Of the 16 pediatric patients, 5 had segmentation failure (31%) in the subaxial spine, and none of the adults did. A form of atlantoaxial dislocation was seen in all cases. On CT imaging, atlantoaxial facets were dislocated in all 41 cases but did not have osseous changes that would have prevented reduction. On MRI, the transverse ligament was identified anterior and inferior to the ossicle and superior to the hypoplastic odontoid process in all cases in which these studies were available (i.e., post-MRI era; 36 of 36 cases). The ligament was hypointense on T2-weighted images but also had an associated hyperintense signal on T2 images. Intraoperatively, the transverse ligament was identified anterior and inferior to the ossicle and superior to the hypoplastic odontoid process in all 41 cases.

CONCLUSIONS

In the largest series to date of irreducible OO and the only study to examine variable factors that lead to irreducibility in OO, the authors found that the position of the transverse ligament anterior and inferior to the ossicle is the most common factor in the irreducibility of OO. The presence of granulation tissue and of the dystopic variant of OO is also associated with irreducibility. The presence of Down syndrome and segmentation failure probably leads to faster progression of ligamentous incompetence and therefore earlier presentation of instability and irreducibility. This is the first study in which intraoperative findings regarding the transverse ligament have been correlated with MRI.