Effects of different gonadotropin pulse frequencies on corpus luteum function during the menstrual cycle of rhesus monkeys.

In the nonfertile menstrual cycle, the frequency of episodic LH secretion declines from approximately 1 pulse/h in the early luteal phase to 1 pulse/4-8 h in the mid- to late luteal phase, but the relevance of this phenomenon to the initiation of functional luteal regression is not completely understood. We investigated whether a reduction in LH pulse frequency causes a decline in luteal progesterone production by experimentally reducing LH pulse frequency during the early luteal phase, and measured the effects on the subsequent plasma progesterone pattern and the onset of luteal regression. Rhesus monkeys were rendered anovulatory by placing radiofrequency lesions in the arcuate region of the medial basal hypothalamus or surgically transecting the hypothalamic-pituitary stalk. Endogenous gonadotropin secretion and ovulatory menstrual cycles were restored by pulsatile infusion of synthetic GnRH at a frequency of 1 pulse/h. Commencing on days 3-6 of the luteal phase, GnRH frequency was changed to either 1 pulse/8 h (four animals) or 1 pulse/24 h (four animals), or maintained at the standard 1 pulse/h frequency (four animals). Luteal phases of 13- to 17-day duration were observed in all animals kept on the 1 pulse/h frequency and in three of four animals in which the frequency was changed to 1 pulse/8 h on day 3 of the luteal phase. Daily midluteal phase (days 5-10) plasma progesterone levels observed in response to the 1 pulse/h and 1 pulse/8 h infusion regimens were similar (mean +/- SE, 4.1 +/- 0.4 vs. 3.2 +/- 0.4 ng/ml; P greater than 0.1). In contrast, short luteal phases were observed in all animals after the LH pulse frequency was reduced to 1 pulse/24 h. Comparison of plasma LH responses to a representative GnRH pulse of each GnRH infusion regimen revealed that the maximal LH levels attained in response to 1 pulse/8 h (47.5 +/- 11.5 ng/ml) were significantly greater (P less than 0.05) than the maximal LH levels attained in response to 1 pulse/h (30.5 +/- 3.2 ng/ml) or 1 pulse/24 h (27.2 +/- 5.0 ng/ml). Progesterone levels remained elevated for 140-200 min after the LH pulse resulting from the 1 pulse/8 h infusion regimen. In response to the 1 pulse/24 h infusion regimen, plasma progesterone levels remained elevated for 60 min after the LH pulse.(ABSTRACT TRUNCATED AT 400 WORDS)

Estrogen induces premature luteal regression in rhesus monkeys during spontaneous menstrual cycles, but not in cycles driven by exogenous gonadotropin-releasing hormone.

Administration of exogenous estradiol during the mid- to late luteal phase of the menstrual cycle results in premature regression of the corpus luteum. The present study was initiated to identify the site of action of estrogen as well as to determine why administration of estrogen during the early luteal phase of the menstrual cycle does not result in luteolysis. Based upon extant literature, we hypothesized that estrogen and progesterone synergize to promote premature luteal regression. We tested this hypothesis in intact, spontaneously cycling rhesus monkeys by inserting estradiol, progesterone, or estrogen plus progesterone capsules on days 2 through 6 of the luteal phase. Insertion of estrogen or progesterone capsules alone did not advance luteolysis compared with the effect of control empty implants (n = 3). In contrast, insertion of estrogen plus progesterone implants on days 2 through 6 of the luteal phase resulted in a significant lowering of serum progesterone concentrations, and menses was advanced 5-6 days compared with control cycles. On the basis of these findings in spontaneously cycling monkeys, we speculated that estrogen treatment causes luteal regression only in the presence of a progesterone-mediated decrease in LH pulse frequency. To test this hypothesis, we used rhesus monkeys whose endogenous gonadotropin secretion was abolished by either placement of radiofrequency lesions in the mediobasal hypothalamus or transection of the hypothalamic-pituitary stalk. Ovulatory menstrual cycles were restored by pulsatile administration of exogenous synthetic GnRH. Insertion of estradiol capsules during the luteal phase into animals whose gonadotropin pulse frequency was set at either one pulse per h or one pulse per 8 h failed to cause premature luteal regression (n = 4). These findings indicate that whereas estrogen promotes luteal regression in intact, spontaneous cycling rhesus monkeys, it does not do so in animals whose gonadotropin secretion is controlled by exogenous GnRH. On the basis of these observations, we conclude that the hypothalamus is a major site of action of estrogen in the initiation of luteal regression in macaques.

Association of an epidermoid tumor with an aneurysm of the anterior communicating artery.

A case of epidermoid tumor enveloping an aneurysm of the anterior communicating artery is reported. Four embryologically similar epithelial tumors of the central nervous system associated with intracranial aneurysms, all craniopharyngiomas, have previously been reported. Theories attempting to relate tumor and aneurysm are discussed. The incidence of aneurysm associated with tumor is difficult to estimate and may be no greater than the probability of their coincidence by chance alone.

Brain abscess complicating the use of a halo orthosis.

We report a case of brain abscess complicating the use of a halo orthosis in the treatment of a cervical spine injury suffered during wrestling. Four previous brain abscesses complicating the use of halo orthoses have been reported. All cases of abscess have been associated with overlying infection at the site of pin insertion. Our case and at least one of those previously reported may have been related to tightening of the halo pins after placement. Serious spine injuries occur rarely in wrestlers and are associated with the use of illegal holds and maneuvers in which one athlete is thrown to the mat. The pathophysiology and radiographic appearance of a unilateral facet dislocation are reviewed.

Postoperative computed tomographic evaluation of patients with large pituitary tumors treated with operative decompression and radiation therapy.

Thirty consecutive patients who underwent operative decompression and radiation therapy for large sellar and suprasellar pituitary tumors (greater than or equal to 2 cm) were studied in terms of the serial computed tomographic (CT) changes. There were 23 men and 7 women. The mean age was 49.6 +/- 2.5 years, and the mean follow-up was 45.3 +/- 3.9 months. Twenty-eight of the 30 patients had transsphenoidal surgery, and 27 had hormonally inactive tumors. Radiation therapy was begun within 1 month of surgery with a mean dose of 4855 +/- 70 cGy. Postoperative CT scans were obtained within 1 month of surgery and at 6- to 12-month intervals thereafter. Fourteen patients (45%) had no suprasellar tumor visualized in either the early postoperative CT scans or on subsequent scans. Eleven patients (35%) had a persistent suprasellar mass during the early postoperative period that resolved on serial CT evaluation. The mean time for resolution was 10.4 +/- 1.2 months. Six patients (20%) had a persistent suprasellar mass on serial CT evaluation. A persistent postoperative mass that subsequently resolved in many of the patients was thought to be caused by the gradual retraction of the postoperative packing and hematoma, as well as the effect of radiation on any residual tumor.

Metastatic tumor of the pituitary gland.

Although metastatic tumors of the pituitary gland and the sellar region are not common, they may radiographically mimic a pituitary tumor. Because the metastasis frequently involves the posterior lobe and because lateral extension to the cavernous sinus is common, patients may present with ptosis, diplopia, or diabetes insipidus. Decrease in anterior pituitary function is less common. Metastatic tumors contain abundant vascular networks, as evidenced by frequent blush on cerebral angiography and increased bleeding at operation. We report the case of a 57-year-old woman who presented with rapid onset of bilateral ptosis and ophthalmoplegia and was found to have a metastatic carcinoma within the pituitary gland.

Monitoring of cortical somatosensory evoked potentials to determine the safety of sacrificing the anterior cerebral artery.

Cortical somatosensory evoked potentials (SSEPs) reflect the functional integrity of somatosensory pathways from the site of stimulation to the primary somatosensory cortex. We used intraoperative monitoring of cortical SSEPs to determine whether the right anterior cerebral artery (RACA), the major feeding vessel of a large arteriovenous malformation (AVM), could be sacrificed without compromising sensorimotor function in the left lower extremity. The SSEPs recorded after test occlusion of the RACA showed preservation of the initial cortical positivity, and the RACA was divided. The AVM was excised completely, and the patient suffered no neurological deficit.

Abscess of the sphenoid sinus after transsphenoidal surgery.

A case of a bacterial abscess developing in the sphenoid sinus 2 weeks after transsphenoidal surgery is presented. Although abscesses within the sella turcica have been reported as rare complications of transsphenoidal surgery, this is the first reported case of the postoperative formation of an abscess of the sphenoid sinus. The patient sought treatment for severe headaches, nausea and vomiting, and marked temperature elevation. A computed tomographic scan demonstrated soft tissue and air within the sphenoid sinus. A regimen of stress doses of hydrocortisone and antibiotics was prescribed, and the patient underwent transsphenoidal drainage of the sphenoid sinus. The sella turcica was not involved. Anaerobic cultures were positive for Fusobacterium necrophorum.

Abscess formation within pituitary tumors.

Three consecutive cases where abscesses were found within pituitary tumors are presented. In all cases, the diagnosis was made preoperatively and the patients were begun on stress doses of hydrocortisone and antibiotics before surgical drainage of the abscess. All patients recovered with minimal neurological deficits. Review of the literature reveals that the diagnosis is seldom made preoperatively or before autopsy and is associated with high mortality and morbidity. Early suspicion of a pituitary abscess leading to early treatment with antibiotics and operative drainage seem to be important factors in decreasing this high mortality and morbidity.

Reversible panhypopituitarism caused by a suprasellar aneurysm: the contribution of mass effect to pituitary dysfunction.

A case of panhypopituitarism and hyperprolactinemia caused by a giant intracranial aneurysm is presented. The case is unique because both the pattern of the pituitary dysfunction and the complete normalization of all pituitary function after decompression of the aneurysm demonstrate the importance of pure compressive effects of mass lesions on pituitary function. The literature regarding return of pituitary function after resection of sellar and suprasellar masses is reviewed, and a schema for classification of pituitary dysfunction caused by mass lesions is proposed.

Endocrine function in patients with large pituitary tumors treated with operative decompression and radiation therapy.

Large pituitary tumors are still a common problem. Thirty consecutive patients underwent operative decompression and radiation therapy for large sellar and suprasellar tumors. They were studied prospectively in terms of their endocrine outcome. Ten of the patients had panhypopituitarism both before and after treatment. The other 20 patients had partial hormonal deficits prior to treatment. Ten (50%) of the 20 patients who had partial preoperative deficits went on to develop delayed onset of worsening in their endocrine function; 9 of the 10 developed panhypopituitarism, and 1 patient developed decreased thyroid function. The mean time from surgery until the onset of delayed worsening in endocrine function was 26.1 months. The mean age of those patients who developed delayed onset of worsening in pituitary function was significantly higher than that of those who did not develop further hormonal loss (40.5 +/- 3.1 years versus 52.0 +/- 4.1 years, P less than 0.05). None of the 10 patients with delayed onset of worsening in pituitary function had anatomical evidence by computed tomographic scan of tumor recurrence. Delayed onset radiation effect is the most likely cause of the late onset of worsening in endocrine function.

Invasive pituitary adenoma with abscess formation: case report.

A case is presented and 10 cases are reviewed in which abscess formation developed in an intrasellar tumor. The diagnosis was made preoperatively or before autopsy in only 1 patient. The mortality rate was greater than 50%. The most common presentation was headache, fever, and visual disturbances with an abnormal sella and sterile cerebrospinal fluid (CSF). Nonconstant findings included meningeal signs and leukocytosis of the CSF. Trans-sphenoidal removal of the tumor and drainage of the abscess with appropriate antibiotic therapy is recommended. (Neurosurgery, 5: 718--722, 1979).

Large and giant paraclinoid aneurysms: surgical techniques, complications, and results.

Twenty-five patients with giant (greater than 25 mm in diameter) and 9 patients with large (15 to 25 mm in diameter) aneurysms of the internal carotid artery in the ophthalmic or paraophthalmic region are reviewed. In 23 of these patients the aneurysm was clipped directly. There was 1 death in this group, and none of the survivors had disabling neurological complications outside the visual system. The other 11 patients were treated by a trapping procedure or by either common carotid ligation or internal carotid ligation in the neck. Of the 5 patients treated by internal carotid ligation preceded by an extracranial to intracranial bypass graft, 3 developed embolic complications, which in 1 patient resulted in death. One of the 4 patients treated by ligation of the common carotid artery died 1 year later from a recurrent subarachnoid hemorrhage. Of the total group, 18 patients had visual loss preoperatively as a result of aneurysmal compression; in 10 the vision was improved by operation, in 3 it was made worse, and in 2 it was unchanged. In another patient the vision continued to deteriorate slowly after common carotid occlusion, and the other 2 patients died postoperatively before vision could be assessed. The complications in the patients are described and analyzed in detail. Maneuvers found to be of value in the direct approach to these lesions are described. Of these, exposure of the internal carotid artery in the neck for temporary occlusion during clipping and thorough drilling of the anterior clinoid process and unroofing of the optic canal were particularly helpful. The literature on indirect methods of treatment by carotid occlusion with and without bypass graft is reviewed with special reference to the complications and effectiveness of each alternative. Based on this review of the literature and our experience, a treatment scheme is suggested for these aneurysms depending on their mode of presentation.

Factors in predicting outcome from operation in patients with prolactin-secreting pituitary adenomas.

Forty female patients with pituitary adenomas were studied retrospectively to determine whether factors could be identified that would help predict outcome from operation. Twenty-five patients had a normal prolactin level (less than or equal to 30 ng/ml) during the early postoperative period (less than or equal to 3 months) and 15 patients had persistent disease (prolactin greater than 30 ng/ml). Nine of the 25 patients who initially had normal prolactin levels during the early postoperative period were found to have elevated prolactin levels during the late postoperative period (greater than 3 months). As has been shown previously, tumor size and preoperative prolactin levels were important factors in predicting surgical outcome. Patients with smaller (Hardy Grades I and II) tumors had significantly better outcome than those with larger (Hardy Grades III and IV) tumors. Patients with successful surgical outcomes had significantly lower preoperative prolactin values (204 ng/ml) than those with operative failures (524 ng/ml). In addition to the known factors, the patient's age at the time of operation, the length of amenorrhea, and the patient's growth hormone response to insulin hypoglycemia were newly identified as factors that helped predict surgical outcome. Patients who were less than or equal to 26 years of age and who had had amenorrhea for less than or equal to 6 years at the time of operation had significantly better surgical outcomes. Patients with normal growth hormone responses to stimulation testing had significantly better surgical outcomes than those with a blunted preoperative growth hormone response. The data suggest that prolactin-secreting pituitary tumors may cause a progressive disorder for which operative cure may be obtained only early in the disease.

Hyponatremia and natriuresis following subarachnoid hemorrhage in a monkey model.

A monkey model of subarachnoid hemorrhage (SAH) was used to study both the incidence of hyponatremia and natriuresis and the associated changes in antidiuretic hormone (ADH) secretion and salt and water balance. Following SAH, seven of nine monkeys became natriuretic and hyponatremic. The natriuretic period lasted an average of 4.4 +/- 0.4 days. The mean nadir of serum sodium content was 125.7 +/- 1.6 mEq/liter, and occurred on the average on the 5th day following SAH. The sodium balance after SAH was negative as compared to the preoperative positive sodium balance (p less than 0.001). The plasma vasopressin level was usually elevated for a day following surgery, but there was no significant difference in the levels during the preoperative period and during the period of natriuresis following SAH. The daily urine output and aldosterone levels were not significantly different, and the plasma volume was slightly, but not significantly, decreased after SAH. Four of the animals that had a hyponatremic and natriuretic response following SAH showed a normal regulation of vasopressin in response to both a water challenge and hypertonic saline challenge. The three monkeys that underwent sham procedures did not become hyponatremic and natriuretic postoperatively. The sham-operated monkeys did not show significant differences in their plasma vasopressin levels, urine volume, plasma volume, and aldosterone levels following surgery. These observations are more consistent with primary natriuresis as the cause of hyponatremia rather than the syndrome of inappropriate secretion of ADH. The cause of the renal loss of sodium is not known, but the possibility of a brain natriuretic factor or an alteration in the neural control of the kidney should be considered.

Symptomatic pituitary tumor enlargement after induced pregnancy. Case report.

A case is presented and 11 others are reviewed in which symptomatic pituitary tumor enlargement occurred during pregnancies that resulted from induced ovulation. The syndrome is usually characterized by headache and visual disturbances with bitemporal visual field abnormalities, but may present with ocular muscle palsies. The cases are divided into two groups. The patients in one group had a shorter duration of amenorrhea (3.8 years), developed symptoms before the 14th week of pregnancy, and were usually treated by tumor removal. Patients in the second group had a longer period of amenorrhea (10.2 years), developed symptoms after the 24th week of pregnancy, and their symptoms regressed with delivery of the infant. Tumor removal or termination of the pregnancy both resulted in resolution of symptoms. All pregnancies resulted in normal infants. This series provides guidelines for management of future cases.

Hyponatremia in intracranial disease: perhaps not the syndrome of inappropriate secretion of antidiuretic hormone (SIADH).

Patients with intracranial disorders are prone to develop hyponatremia with inability to prevent the loss of sodium in their urine. This was originally referred to as "cerebral salt wasting," but more recently is thought to be secondary to the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Blood volume determinations were made in 12 unselected neurosurgical patients with intracranial disease who fulfilled the laboratory criteria for SIADH. Ten of the 12 patients had significant decreases in their red blood cell mass, plasma volume, and total blood volume. The finding of a decreased blood volume in patients who fulfill the laboratory criteria for SIADH is better explained by the original concepts of cerebral salt wasting than by SIADH. The primary defect may be the inability of the kidney to conserve sodium.

Fluid and electrolyte balance during a cool weather marathon.

Changes in blood, serum, and urine parameters that are usually associated with fluid and electrolyte balance were studied in 45 volunteers who ran the 1987 Pittsburgh Marathon. There were 39 males and 6 females. The mean age was 39.3 years. Their mean fluid intake was 1650 cc and the mean finishing time was 4 hours and 1 minute. The race was run in the rain with a temperature of 46 degrees F. When the prerace and postrace values of the runners were compared, significant increases were noted in the serum sodium, potassium, blood urea nitrogen (BUN), creatinine, uric acid, creatine phosphokinase (CPK), protein, plasma renin, vasopressin, and urinary potassium. Significant decreases were found in weight, blood pressure, and urinary sodium. No significant differences were noted in serum chloride, serum glucose, and hemoglobin/hematocrit. The mean weight loss of 1.9 kg was less than weight losses reported in marathons run under warmer conditions.

A technique of clipping giant intracranial aneurysms with the preservation of the parent artery.

Several methods are currently available for the treatment of giant intracranial aneurysms. In this report, we emphasize the technique of temporary trapping of the aneurysm followed by aspiration and collapse, and subsequent clipping. This method permits the preservation of the parent vessel and avoids the need for creating a microvascular bypass. Two cases are presented to illustrate this technique; in one case the patient had a giant middle cerebral artery aneurysm, and in the other a giant carotid-ophthalmic artery aneurysm. Both aneurysms were successfully clipped with preservation of the major vessels and a good result. On the basis of the configurations of their necks, giant aneurysms can be classified into three groups. The different methods of treating these aneurysms are reviewed with respect to this classification.

Gap detection as a function of stimulus loudness for listeners with and without hearing loss.

Temporal resolution, or the ability to process rapidly changing stimuli, has been purported to be reduced in some listeners with hearing loss while being described as normal in others. Ensuring stimulus audibility by increasing stimulus levels results in near-normal temporal resolution abilities for many listeners with hearing loss, but may also result in uncomfortably loud stimulus levels. The current study was conducted to describe temporal resolution abilities of listeners with and without hearing loss as a function of stimulus loudness. The gap detection abilities of 8 listeners with normal hearing were compared with those of 8 listeners with mild to moderate hearing losses over a wide range of intensities using a 650-Hz wide high-frequency noise marker. At low intensities, listeners with hearing loss show poor gap detection ability. As intensity increases, most listeners' performance improves and stabilizes near normal at high loudness and sensation levels. At comfortable loudness, gap detection abilities of listeners with hearing loss are less than at loud levels and are considerably poorer than normal.