Idiopathic intracranial hypertension is common in obese women and can lead to significant visual impairment. First described more than 100 years ago, the cause of the disorder remains unknown. Despite a multitude of proposed links, the aetiology has never been established. Impairment of cerebrospinal-fluid reabsorption is the most likely underlying pathophysiological cause of the raised pressure, but this notion has yet to be proven. Cerebral venous sinus abnormalities associated with the disorder need further exploration. Although the major symptoms of headache and visual disturbance are well documented, most data for disease outcome have been from small retrospective case series. No randomised controlled trials of treatment have been done and the management is controversial. The importance of weight loss needs clarification, the role of diuretics is uncertain, and which surgical intervention is the most effective and safe is unknown. Prospective trials to examine these issues are urgently needed.

https://www.thelancet.com/pdfs/journals/laneur/PIIS1474-4422(06)70442-2.pdf

Idiopathic intracranial hypertension

To the Editor:

We congratulate Farb et al. on their discovery, introduction, and use of the auto-triggered elliptic-centric-ordered three-dimensional gadolinium-enhanced MR venogram (ATECO MRV) to diagnose idiopathic intracranial hypertension (IIH) with unprecedented sensitivity and specificity.1 The similarities between IIH and cerebral venous thrombosis (CVT) and their established pathophysiologic tie to cranial venous outflow obstruction are clear and may change the way we diagnose and treat these conditions. CVT and IIH overlap in risk factor profiles and in their relation to hyperestrogenemic exacerbation. It was recently found that both have a high incidence of hypercoagulable states and systemic inflammatory disease is recognized.2–4⇓⇓ CVT has long been considered to mimic or masquerade as IIH and is frequently underdiagnosed.2,5⇓ The increased incidence of CVT has allowed the detection of increasingly smaller venous flow abnormalities or thrombus and has paralleled the advent of the conventional CT and MRI scanners.3 It appears that the ATECO MRV has jumped the barrier and found consistent flow abnormality without radiologically confirmed thrombus in patients with IIH. Although it is unclear if cranial venous outflow obstruction is the primary or a secondary process in IIH, the following question is raised: “Is it time to approach these two conditions as a spectrum of the same disease process?”

Bousser et al. have established heparin anticoagulation as the gold standard of treatment for CVT.2 Heparin is now advocated in CVT patients regardless …

Idiopathic intracranial hypertension The prevalence and morphology of sinovenous stenosis

✓ Sixty-one patients treated with C1–2 transarticular screw fixation for spinal instability participated in a detailed clinical and radiological study to determine outcome and clarify potential hazards. The most common condition was rheumatoid arthritis (37 patients) followed by traumatic instability (15 patients). Twenty-one of these patients (onethird) underwent either surgical revision for a previously failed posterior fusion technique or a combined anteroposterior procedure. Eleven patients underwent transoral odontoidectomy and excision of the arch of C-1 prior to posterior surgery. No patient died, but there were five vertebral artery (VA) injuries and one temporary cranial nerve palsy. Screw malposition (14% of placements) was comparable to another large series reported by Grob, et al. There were five broken screws, and all were associated with incorrect placement. Anatomical measurements were made on 25 axis bones. In 20% the VA groove on one side was large enough to reduce the width of the C-2 pe...

Radiological and anatomical evaluation of the atlantoaxial transarticular screw fixation technique

Objective We review our experience with the use of the plate and screw method of fixation in the treatment of 160 patients with atlantoaxial instability during a 14-year period at our center We previously described this method of fixation in 1994 Methods Between 1988 and 2001, 160 patients with atlantoaxial instability were treated with the use of a plate and screw method of fixation at the Department of Neurosurgery at King Edward Memorial Hospital in Bombay, India The study group was composed of 91 males and 69 females (mean age, 23 yr; age range, 18 mo-79 yr) Atlantoaxial instability was a result of congenital abnormality in 132 patients (83%) and occurred after trauma in 28 patients (17%) All patients had mobile, completely reducible atlantoaxial dislocation For 3 months postoperatively, a hard cervical collar was used The mean follow-up period was 42 months (range, 4 mo-14 yr) Results Three patients died in the postoperative phase Successful stabilization of the atlantoaxial region was documented with dynamic radiography in the other 157 patients There was no incidence of implant rejection In one patient, one screw was found to be broken 18 months after surgery; however, firm bony fusion was documented in this patient There were no neurological, vascular, or infective complications Conclusion The plate and screw method of fixation with the use of intra-articular bone grafts in patients with atlantoaxial instability yielded a 100% fusion rate with a low incidence of complications

Atlantoaxial fixation using plate and screw method: a report of 160 treated patients.

A system for accessing a surgical target site and related methods, involving an initial distraction system for creating an initial distraction corridor, and an assembly capable of distracting from the initial distraction corridor to a secondary distraction corridor and thereafter sequentially receiving a plurality of retractor blades for retracting from the secondary distraction corridor to thereby create an operative corridor to the surgical target site, both of which may be equipped with one or more electrodes for use in detecting the existence of (and optionally the distance and/or direction to) neural structures before, during, and after the establishment of an operative corridor to a surgical target site.

Surgical Access System and Related Methods

Pseudotumor cerebri (PTC), or idiopathic intracranial hypertension, is a syndrome associated with multiple clinical conditions. We hypothesize that most if not all etiologies result in an increase in intracranial venous pressure as a final common pathway. We studied 10 patients with PTC. Five had dural venous outflow obstruction as demonstrated by venography, and the five remaining patients had normal venous anatomy. Pressure measurements, made during venography in eight patients, all showed elevated pressures. Pressure measurements in the superior sagittal sinus ranged from 13 to 24 mm Hg (mean, 16.6 mm HG). Patients with obstruction tended to have a high pressure gradient across the stenotic segment. Five patients with normal dural venous anatomy had elevated right atrial pressures (range, 6 to 22 mm Hg; mean, 11.8 mm Hg), which were transmitted up to the intracranial venous sinuses. Endovascular techniques, including angioplasty and infusion of thrombolytic agents in some cases, improved outlet obstruction from a hemodynamic perspective but were ineffective in consistently and reliably alleviating the clinical manifestations of PTC. Patients in both groups tended to respond well to conventional CSF diversion procedures. Our study suggests that elevated intracranial venous pressure may be a universal mechanism in PTC of different etiologies. This elevated venous pressure leads to elevation in CSF and intracranial pressure by resisting CSF absorption. Although the mechanism leading to venous hypertension in the presence of outflow obstruction is obvious, the etiology of increased intracranial and central systemic venous pressure in PTC remains obscure.

Elevated intracranial venous pressure as a universal mechanism in pseudotumor cerebri of varying etiologies

✓ Eighteen patients with atlantoaxial instability were treated with posterior atlantoaxial facet screws to obtain immediate rigid fixation of C1–2. Of these 18 patients, instability occurred due to trauma in nine, rheumatoid arthritis in six, neoplasms in two, and os odontoideum in one. Four patients presented with nonunion after failed C1–2 wire and graft procedures. In all cases in this series the screw fixations were augmented with an interspinous C1–2 strut graft which was wired in place to provide three-point stabilization and to facilitate bone fusion. In every case fixation was satisfactory, and C1–2 alignment and stability were restored without complications due to instrumentation. One patient died 3 months postoperatively from metastatic tumor; the spinal fixation was intact. All 17 surviving patients have developed osseous unions (mean follow-up period 12 months, range 6 to 16 months). Posterior atlantoaxial facet screw fixation provides immediate multidirectional rigid fixation of C1–2 that is ...

Posterior atlantoaxial facet screw fixation

Object. The goal of this study was to review retrospectively the outcome of 95 patients with various disorders leading to instability of the thoracolumbar and lumbar spine who were treated consecutively via a posterior surgical approach with pedicle screw fixation in which the Texas Scottish Rite Hospital system was used. Methods. All cases were managed according to the same protocol. Follow-up review averaged 29.6 months. Radiographic evidence of osseous union and the patient's current status were analyzed. Four screws were malpositioned, and there were two dural lacerations of a nerve root and one pedicle fracture. Deep wound infections developed in five patients (5.2%), and three patients had postoperative radicular pain. In one case, the rods disengaged from the screws; in four cases, hardware was removed but there were no broken screws. Neurological deficits improved in 85% of the surviving patients, and no patient was worse neurologically after surgery. The rate of osseous union was 96.8%. Three pat...

Efficacy of pedicle screw fixation in the treatment of spinal instability and failed back surgery: a 5-year review.

An expandable medical implant for supporting bone structures is disclosed. The implant may include an outer member and an inner member receivable in the outer member. One of the outer and inner members includes a tapered surface and the other of the outer and inner members includes a scalloped surface. The implant may also include a locking element disposed between the tapered surface and the scalloped surface. The tapered surface may be movable relative to the locking element to transversely shift the locking element into engagement with the scalloped surface to inhibit a decrease in the overall implant height.

Expanding vertebral body implant

A motion-sensing mechanism is provided that facilitates numerous aspects of the medical industry. In one aspect, the motion-sensing mechanism is used to track instruments and personnel in a field of view relative to a patient such that the instrument or personnel may be displayed on a heads-up display showing a model of the patient's anatomy. In another aspect, the motion-sensing mechanism makes a reference image of a patient, visitor, or staff such that when the subject of the reference images passes another (or the same) motion-sensing mechanism, the identity of the subject is determined or recognized. In still other aspects, the motion-sensing mechanism monitors motion of a portion of a patient's anatomy and compares the same to an expected motion for diagnostic evaluation of pain generators, physical therapy effectiveness, and the like.

Dean G. Karahalios

Papers

Elevated intracranial venous pressure as a universal mechanism in pseudotumor cerebri of varying etiologies

Posterior atlantoaxial facet screw fixation

Efficacy of pedicle screw fixation in the treatment of spinal instability and failed back surgery: a 5-year review.

Expanding vertebral body implant

Surgical and Medical Instrument Tracking Using a Depth-Sensing Device