H. Richard Winn, John A. Jane, James Taylor, Donald Kaiser and Gavin W. Britz
Object. The prevalence of unruptured cerebral aneurysms is unknown, but is estimated to be as high as 5%. The goal of this study was to determine the prevalence of asymptomatic incidental aneurysms.
Methods. The authors studied all cerebral arteriography reports produced at a single institution, the University of Virginia, between April 1969 and January 1980. A review of 3684 arteriograms demonstrated 24 cases of asymptomatic aneurysms, yielding a prevalence rate of 0.65%. The majority (67%) of the 24 patients harboring unruptured aneurysms were women. More than 90% of the unruptured aneurysms were located in the anterior circulation and in locations similar to those found in patients with ruptured aneurysms. Nearly 80% of the aneurysms were smaller than 1 cm in their greatest diameter. The frequency of asymmetrical unruptured aneurysms (0.6–1.5%) was constant throughout all relevant age ranges (35–84 years).
Conclusions. While keeping in mind appropriate caveats in extrapolating from these data, the prevalence rate of asymptomatic unruptured aneurysms found in the present study allows an estimation of the yearly rate of rupture of these lesions. The authors suggest that this yearly rate of rupture falls within the range of 1 to 2%.
Assessment of risk in a series of 610 patients
Ralph G. Dacey Jr., Wayne M. Alves, Rebecca W. Rimel, H. Richard Winn and John A. Jane
✓ A small number of patients with an apparently minor head injury will develop a life-threatening intracranial hematoma that must be rapidly detected and removed. To assess the risk of a significant intracranial neurosurgical complication after apparently minor head injury, the authors collected data prospectively on 610 patients who had sustained a transient posttraumatic loss of consciousness or other neurological function and who had a Glasgow Coma Scale (GCS) score of 13, 14, or 15 in the emergency room. Skull x-ray films were obtained in 583 patients, 66 of whom (10.8% of the study population) had cranial fractures. Eighteen of the 610 patients (3.0%) required a neurosurgical procedure. Three acute subdural hematomas, one epidural hematoma, and one traumatic intracerebral hematoma required craniotomy. Of the 66 patients who had skull fracture, 7.6% required a craniotomy for intracranial hematoma. Thirteen (19.7%) of the 66 patients with skull fracture required an operative procedure as compared to five (1.0%) of the 517 patients without skull fracture. Two patients with a normal GCS score of 15 and normal skull x-ray films subsequently underwent operative treatment.
The cost of three alternative management schemes for these patients was estimated. A 50% reduction in cost of management could be effected by the use of computerized tomography (CT) scans (or possibly skull x-ray films) in determining which of the patients who are alert at the time of presentation should be admitted for observation. Several other conclusions can be drawn from this study. First, an initial GCS score between 13 and 15 does not necessarily indicate that a patient has sustained a trivial head injury, since 3% of such patients will require an operative procedure despite an initially normal level of alertness. Second, an abnormal skull x-ray film increases by a factor of 20 the probability that a patient will need neurosurgical treatment. Third, it is very unusual for patients who have a GCS score of 15 and a normal skull x-ray film to have a significant neurosurgical complication. Fourth, the alternative management schemes that depend on selective use of skull films and CT scans may significantly reduce the cost of caring for patients with minor head injury.
John A. Jane, Neal F. Kassell, James C. Torner and H. Richard Winn
✓ The authors summarize the findings of previous studies relating to the natural history of aneurysms and arteriovenous malformations (AVM's). Ruptured aneurysms have their highest rate of rebleeding on Day 1, and at least 50% will rebleed during the 6 months after the first hemorrhage. Thereafter, the rate drops to at least 3% a year. This is the same rate as seen in anterior and posterior communicating artery aneurysms treated by anterior cerebral artery clipping and carotid ligation; these operations provide immediate protection but do not result in long-term diminution of the risk of rebleeding. Patients with unruptured incidental and unruptured multiple aneurysms rebleed at a rate of 1% per year, as do patients with subarachnoid hemorrhage of unknown etiology. The risk of rebleeding for AVM's is 3% a year.
Incidence of late hemorrhage and implications for treatment of incidental aneurysms
H. Richard Winn, Waled S. Almaani, Sarah L. Berga, John A. Jane and Alan E. Richardson
✓ The proper treatment of multiple and incidental aneurysms remains controversial because the long-term result of different modes of management is unclear. This report evaluates the long-term outcome (follow-up period averaged 7.7 years) in 182 patients with multiple aneurysms who suffered a subarachnoid hemorrhage (SAH) to document the incidence of late bleeding. Of the 182 patients, 132 were treated by bed rest and 50 by surgery (craniotomy) directed at only the ruptured aneurysm. Seventy of the patients with bed rest were alive after 6 months. Twenty-one of these conservatively treated patients (30%) suffered a late hemorrhage, which is equal to the previously reported average yearly rebleed rate (3%) with a single aneurysm of the anterior circulation. There was no evidence that a previously intact aneurysm had ruptured in SAH patients treated with bed rest, indicating that late hemorrhage was due to rerupture from the original aneurysm. Patients who were hypertensive and who had a large aneurysm had an increased risk of late rehemorrhage. A linear discriminant analysis was developed to predict late rebleeding. The fate of intact aneurysms was evaluated by following patients with multiple aneurysms treated by craniotomy directed only at the ruptured aneurysm. Of the 50 craniotomy patients, 38 were alive after 6 months. In this group, the minimal risk of rupture of an intact aneurysm is approximately 1% per year. The presence of hypertension increased the risk of late hemorrhage. In conclusion, patients with multiple untreated aneurysms managed by bed rest have a late rehemorrhage rate equal to that observed in patients with a single cerebral aneurysm; the data indicate that rupture of intact aneurysms is not insignificant.
William J. Babler, John A. Persing, H. Richard Winn, John A. Jane and George T. Rodeheaver
✓ Premature closure of a cranial suture results in skull deformation characterized by inhibited skull growth in a direction perpendicular to the course of the affected suture. Early surgical release of the closed suture results in a “normal” skull morphology. The present experimental study measured alterations in growth at the transverse cranial sutures that occurred following induced premature closure of the coronal suture and its subsequent release in New Zealand White rabbits. Using roentgenocephalometric methods, growth and morphometric changes were monitored at the frontonasal, coronal, and anterior lambdoid sutures following premature closure of the coronal suture at 9 days of age. The results indicated that premature closure of the coronal suture did not result in compensatory (increased) growth at the other transverse sutures of the vault. In fact, growth at these sutures was significantly reduced. This reduced growth at adjacent transverse sutures was not ameliorated by early surgical release of the fused suture.
David D. Weaver, H. Richard Winn and John A. Jane
✓ Four patients with unilateral mass lesions are presented in whom bilateral supratentorial subarachnoid pressures were continuously recorded. A significant pressure differential between the ipsi- and contralateral side was documented in each case. The possible relationship of this phenomenon to various factors involved in producing increased intracranial pressure, including cerebrospinal fluid flow dynamics, vascular reactivity, elasticity, and brain tissue pressure, are discussed. This study suggests that supratentorial subarachnoid pressure should be measured ipsilateral to the site of a focal mass lesion.
William J. Babler, John A. Persing, K. Maurits Persson, H. Richard Winn, John A. Jane and George T. Rodeheaver
✓ Using radiocephalometric procedures, the authors examined the separate effects of suturectomy, periostectomy, and dural transection on the growing skull in young rabbits. When the coronal suture was surgically removed during normal growth, the freed frontal and parietal bones separated at a significantly accelerated rate. No accelerated separation was found when only the overlying periosteum and aponeurosis were transected. Furthermore, no additional separation was observed when the dura mater and falx cerebri were transected following suturectomy. Analysis of growth at the adjacent frontonasal and anterior lambdoid sutures suggested that the accelerated separation of bones after suturectomy was compensated for by reduced growth at these adjacent sutures. The result of these compensatory actions was that the total length of the skull remained unchanged. This study not only supports earlier observations that sutures grow in response to extrinsic separative forces but, significantly, that the suture tissue itself, rather than the dura or pericranium, acts as a restraint during normal translatory growth.
Rebecca W. Rimel, Albert B. Butler, H. Richard Winn, Tae Sung Park, George W. Tyson and John A. Jane
✓ New skeletal tongs have been designed which offer a significant design advance over previously available models. The University of Virginia tongs combine the ease of application and increased weight-handling abilities of the Gardner-Wells tongs with the patient mobility allowed by the Crutchfield tongs.