Saccular influence on the otolith-spinal reflex and posture during sudden falls of the cat.

HYPOTHESIS: The saccule provides important input for the otolith spinal reflex during sudden falls in the cat. BACKGROUND: Previous studies on cats have identified two distinct components of muscle activity in response to sudden falls: an early otolith-dependent component (OSR) and a later nonlabyrinthine component associated with landing. The presence of an otolith-dependent reflex suggests a discrete role of the otolith organs in the control of posture and locomotion. METHODS: The influence of saccular input on the OSR during sudden falls was studied by simultaneous video and electromyographic (EMG) recordings obtained from saccular-deficient deaf white cats and white cats with normal hearing. RESULTS: A total of 628 sudden falls from five cats (two normal, one unilaterally deaf and two bilaterally deaf) were studied. Normal cats had a total of 337 drops, 276 of which (82%) were acceptable; a unilaterally deaf cat had a total of 79 drops, 56 of which (71%) were acceptable; deaf cats had a total of 212 drops, 177 of which (83%) were acceptable. The earliest of five observed behavioral events was that of forelimb extension which had a mean latency of 98 +/- 32 msec in normal cats and 139 +/- 28 msec in deaf cats (p < 0.0001). The mean latency of early EMG activity in normal cats was 19 +/- 7 msec and in deaf cats was 30 +/- 13 msec (p < 0.0001). The unilaterally deaf cat exhibited behavior and early EMG responses that were similar to those of normal cats. Deaf cats displayed poor body control during landings that improved with experience. CONCLUSIONS: These data demonstrate that the saccule provides important input for the otolith spinal reflex in the cat, and cats that lack both saccules have discernible behavioral and EMG differences in response to sudden falls, when compared with normal cats.

Family-centered care of the critically III neurologic patient.

To determine the immediate needs of families of neurological/neurosurgical patients during the critical care period, family members were interviewed, using a 45 needs statement inventory and an open-ended questionnaire. Each participant addressed all the needs statements and 70% answered the open-ended questions. The participants ranked "to be assured that the best care is being given to the patient" as their number one need. Sixty percent of the participants ranked the physician as the most likely person to meet their needs. When compared, no significant difference was found between the families of neurological/neurosurgical and cardiac/MI patients. Although ranked slightly differently, 13 of the top 15 needs for both groups were the same. The two top needs were ranked in reverse order, "to be assured that the best possible care is being given to the patient," and "to have questions answered honestly," respectively. Nurses caring for the neurological/neurosurgical patients need to be aware that, for the most part, the top needs for families of this group have centered around communication, honesty, and reassurance. Participants do not want to hear false hopes. The family perceived the nurses as giving information regarding transfer and day-to-day occurrences with the patient care.

Electrophysiologic studies on locked-in patients: heterogeneity of findings.

Somatosensory evoked potentials, brain-stem auditory evoked potentials and electroencephalograms were obtained from 9 patients with the diagnosis of 'locked-in' syndrome. No pattern of evoked potential abnormality was specific to this syndrome, with findings ranging from bilaterally normal to unilaterally or bilaterally absent. The evoked potential studies complemented radiographic findings in defining the extent of the lesion and revealed that a portion of the pontine tegmentum was usually involved. Pathology from 2 patients corroborated the findings of the evoked potential studies. The value of evoked potential studies of patients with locked-in syndrome is to provide early objective evidence of brain-stem involvement independent of the clinical examination, EEG and radiographic studies.

The somatosensory evoked potential as a noninvasive method to determine flow rates for hyperosmotic disruption of the blood-brain barrier.

We have developed a noninvasive method to determine the flow rates necessary to produce hyperosmotic blood-brain barrier disruption in individual animals. The method uses the intracarotid infusion of 0.9% NaCl at increasing flow rates, while concurrently measuring the amplitude of the somatosensory evoked potential (SSEP). For these studies, dogs were prepared with craniotomies to visualize the duration of cortical blanching. Saline (0.9% NaCl) was infused into the internal carotid artery at flow rates of 0.9 to 2.1 ml/s for periods from 2 to 40 seconds while the SSEP was concurrently measured in six 30-second epochs before, during, and after the infusion. There was a linear relationship between the duration of cortical blanching (from 2 to 30 seconds) and amplitude suppression of the major negative deflection of the SSEP. This relationship allowed us to predict the intracarotid infusion rate necessary to achieve cortical blanching for periods of 20 seconds or more. Subsequent infusion of 1.4 or 1.6 osmolar mannitol at the predicted flow rate resulted in more pronounced suppression of the SSEP than did 0.9% NaCl and produced disruption of the blood-brain barrier as documented by computed tomographic scans with contrast enhancement. Intracarotid infusions of 0.9% NaCl that produced partial blanching (partial replacement of blood in cortical vessels) were associated with paradoxical enhancement of SSEP amplitude, thus providing an additional measure of the adequacy of the infusion rate. This technique provides a reliable method to determine intracarotid infusion rates for hyperosmotic disruption of the blood-brain barrier in individual animals, before the intracarotid infusion of hyperosmolar solutions.

Laser-assisted nerve repair in primates.

Studies on the peripheral nerves in rats and other species have helped in the development of laser-assisted nerve anastomosis (LANA), but offer little in evaluating the efficacy of this technique in primates. The authors present a study of LANA in the peripheral nerves of rhesus monkeys. Twelve adult rhesus monkeys underwent bilateral resection of a portion of the peroneal nerve followed by placement of autogenous sural nerve interposition fascicular grafts. The grafts were completed with conventional microsurgical suture technique on one side and with LANA on the other. At 5, 8, 10, and 12 months, the grafted nerves were evaluated for continuity, nerve conduction, and histology (both light and electron microscopy). No significant difference in continuity, conduction velocity, nerve degeneration, nerve regeneration, axon fiber number, or axon fiber density was found in any animal between grafts performed by conventional microsuture and LANA grafts. There was no difference in distal or proximal myelinated fiber density between the LANA grafts and the conventional microsuture grafts. It was concluded that LANA is as effective as microsurgical suture nerve anastomosis in a primate model of nerve repair and grafting.

Tethered cervical spinal cord. Case report.

A case of congenital tethered cervical spinal cord is presented in a young adult. Metrizamide computerized tomography was the most useful imaging technique for identifying the tethered spinal cord. Intraoperative somatosensory evoked potentials correlated well with clinical improvement following surgery.

Motor neuron disease: decremental responses to repetitive nerve stimulation.

We found significant decrement of the compound muscle action potential recorded from the abductor digiti minimi muscle in response to repetitive nerve stimulation in patients with rapidly developing motor neutron disease (MND), but not in patients with slowly developing disease when measured before exercise (7.6 plus or minus 1.3% versus 1.6 plus or minus 1.6%) and 2 minutes after exercise (13.6 plus or minus 1.2% versus 0.5 plus or minus 0.5%). All patients showed repair of decrement immediately after exercise. The mean amplitude of the compound muscle action potential was significantly lower in both the rapid-disease (2.9 plus or minus 0.9 mV) and slow-disease (5.2 plus or minus 1.6 mV) groups than in controls (14.5 plus or minus 1.2 mV). For individual patients, there was no correlation between amplitude of the compound muscle action potential and decrement. These data indicate that decrement in MND relates to activity of disease of the motor neuron.

Eaton-Lambert syndrome in a 9-year-old girl.

A girl with Eaton-Lambert syndrome had symptoms beginning at the age of 9 years. An extensive search for underlying neoplasm or definable autoimmune disease gave negative findings.