Critical and Ictal Phases in Simulated EEG Signals on a Small-World Network

Healthy brain function is marked by neuronal network dynamics at or near the critical phase, which separates regimes of instability and stasis. A failure to remain at this critical point can lead to neurological disorders such as epilepsy, which is associated with pathological synchronization of neuronal oscillations. Using full Hodgkin-Huxley (HH) simulations on a Small-World Network, we are able to generate synthetic electroencephalogram (EEG) signals with intervals corresponding to seizure (ictal) or non-seizure (interictal) states that can occur based on the hyperexcitability of the artificial neurons and the strength and topology of the synaptic connections between them. These interictal simulations can be further classified into scale-free critical phases and disjoint subcritical exponential phases. By changing the HH parameters, we can model seizures due to a variety of causes, including traumatic brain injury (TBI), congenital channelopathies, and idiopathic etiologies, as well as the effects of anticonvulsant drugs. The results of this work may be used to help identify parameters from actual patient EEG or electrocorticographic (ECoG) data associated with ictogenesis, as well as generating simulated data for training machine-learning seizure prediction algorithms.

Hospital Length of Stay and Readmission Rate for Neurosurgical Patients

BACKGROUND

Hospital readmission rate has become a major indicator of quality of care, with penalties given to hospitals with high rates of readmission. At the same time, insurers are increasing pressure for greater efficiency and reduced costs, including decreasing hospital lengths of stay (LOS).

OBJECTIVE

To analyze the authors' service to determine if there is a relationship between LOS and readmission rates.

METHODS

Records of patients admitted to the authors' institution from October 2007 through June 2014 were analyzed for several data points, including initial LOS, readmission occurrence, admitting and secondary diagnoses, and discharge disposition.

RESULTS

Out of 9409 patient encounters, there were 925 readmissions. Average LOS was 6 d. Univariate analysis indicated a higher readmission rate with more diagnoses upon admission (P < .001) and an association between insurance type and readmission (P < .001), as well as decreasing average yearly LOS (P = .0045). Multivariate analysis indicated statistically significant associations between longer LOS (P = .03) and government insurance (P < .01).

CONCLUSION

A decreasing LOS over time has been associated with an increasing readmission rate at the population level. However, at the individual level, a prolonged LOS was associated with a higher risk of readmission. This was attributed to patient comorbidities. However, this increasing readmission rate may represent many factors including patients' overall health status. Thus, the rate of readmission may represent a burden of illness rather than a valid metric for quality of care.

Synchronized Beta-Band Oscillations in a Model of the Globus Pallidus-Subthalamic Nucleus Network under External Input

Hypokinetic symptoms of Parkinson's disease are usually associated with excessively strong oscillations and synchrony in the beta frequency band. The origin of this synchronized oscillatory dynamics is being debated. Cortical circuits may be a critical source of excessive beta in Parkinson's disease. However, subthalamo-pallidal circuits were also suggested to be a substantial component in generation and/or maintenance of Parkinsonian beta activity. Here we study how the subthalamo-pallidal circuits interact with input signals in the beta frequency band, representing cortical input. We use conductance-based models of the subthalamo-pallidal network and two types of input signals: artificially-generated inputs and input signals obtained from recordings in Parkinsonian patients. The resulting model network dynamics is compared with the dynamics of the experimental recordings from patient's basal ganglia. Our results indicate that the subthalamo-pallidal model network exhibits multiple resonances in response to inputs in the beta band. For a relatively broad range of network parameters, there is always a certain input strength, which will induce patterns of synchrony similar to the experimentally observed ones. This ability of the subthalamo-pallidal network to exhibit realistic patterns of synchronous oscillatory activity under broad conditions may indicate that these basal ganglia circuits are directly involved in the expression of Parkinsonian synchronized beta oscillations. Thus, Parkinsonian synchronized beta oscillations may be promoted by the simultaneous action of both cortical (or some other) and subthalamo-pallidal network mechanisms. Hence, these mechanisms are not necessarily mutually exclusive.

Stereotactic Radiosurgery and Fractionated Stereotactic Radiotherapy in the Treatment of Uveal Melanoma

Uveal melanoma is the most common primary intraocular malignant tumor. Radiation therapy has now replaced enucleation as the treatment of choice, with radioactive eye plaques and proton therapy being the two most studied radiotherapy modalities. More recently, stereotactic radiosurgery and fractionated stereotactic radiotherapy have emerged as promising, non-invasive treatments for uveal melanoma. This review summarizes the available literature on these newer treatment modalities.

Interaction of synchronized dynamics in cortex and basal ganglia in Parkinson's disease

Parkinson's disease pathophysiology is marked by increased oscillatory and synchronous activity in the beta frequency band in cortical and basal ganglia circuits. This study explores the functional connections between synchronized dynamics of cortical areas and synchronized dynamics of subcortical areas in Parkinson's disease. We simultaneously recorded neuronal units (spikes) and local field potentials (LFP) from subthalamic nucleus (STN) and electroencephalograms (EEGs) from the scalp in parkinsonian patients, and analysed the correlation between the time courses of the spike-LFP synchronization and inter-electrode EEG synchronization. We found the (non-invasively obtained) time course of the synchrony strength between EEG electrodes and the (invasively obtained) time course of the synchrony between spiking units and LFP in STN to be weakly, but significantly, correlated with each other. This correlation is largest for the bilateral motor EEG synchronization, followed by bilateral frontal EEG synchronization. Our observations suggest that there may be multiple functional modes by which the cortical and basal ganglia circuits interact with each other in Parkinson's disease: not only may synchronization be observed between some areas in cortex and the basal ganglia, but also synchronization within cortex and within basal ganglia may be related, suggesting potentially a more global functional interaction. More coherent dynamics in one brain region may modulate or activate the dynamics of another brain region in a more powerful way, causing correlations between changes in synchrony strength in the two regions.

A flexible platform for biofeedback-driven control and personalization of electrical nerve stimulation therapy

Electrical vagus nerve stimulation is a treatment alternative for many epileptic and depressed patients whose symptoms are not well managed with pharmaceutical therapy. However, the fixed stimulus, open loop dosing mechanism limits its efficacy and precludes major advances in the quality of therapy. A real-time, responsive form of vagus nerve stimulation is needed to control nerve activation according to therapeutic need. This personalized approach to therapy will improve efficacy and reduce the number and severity of side effects. We present autonomous neural control, a responsive, biofeedback-driven approach that uses the degree of measured nerve activation to control stimulus delivery. We demonstrate autonomous neural control in rats, showing that it rapidly learns how to most efficiently activate any desired proportion of vagal A, B, and/or C fibers over time. This system will maximize efficacy by minimizing patient response variability and by minimizing therapeutic failures resulting from longitudinal decreases in nerve activation with increasing durations of treatment. The value of autonomous neural control equally applies to other applications of electrical nerve stimulation.

Basal ganglia modulation of thalamocortical relay in Parkinson's disease and dystonia

Basal ganglia dysfunction has being implied in both Parkinson's disease and dystonia. While these disorders probably involve different cellular and circuit pathologies within and beyond basal ganglia, there may be some shared neurophysiological pathways. For example, pallidotomy and pallidal Deep Brain Stimulation (DBS) are used in symptomatic treatment of both disorders. Both conditions are marked by alterations of rhythmicity of neural activity throughout basal ganglia-thalamocortical circuits. Increased synchronized oscillatory activity in beta band is characteristic of Parkinson's disease, while different frequency bands, theta and alpha, are involved in dystonia. We compare the effect of the activity of GPi, the output nuclei of the basal ganglia, on information processing in the downstream neural circuits of thalamus in Parkinson's disease and dystonia. We use a data-driven computational approach, a computational model of the thalamocortical (TC) cell modulated by experimentally recorded data, to study the differences and similarities of thalamic dynamics in dystonia and Parkinson's disease. Our analysis shows no substantial differences in TC relay between the two conditions. Our results suggest that, similar to Parkinson's disease, a disruption of thalamic processing could also be involved in dystonia. Moreover, the degree to which TC relay fidelity is impaired is approximately the same in both conditions. While Parkinson's disease and dystonia may have different pathologies and differ in the oscillatory content of neural discharge, our results suggest that the effect of patterning of pallidal discharge is similar in both conditions. Furthermore, these results suggest that the mechanisms of GPi DBS in dystonia may involve improvement of TC relay fidelity.

Intermittent neural synchronization in Parkinson's disease

Motor symptoms of Parkinson's disease are related to the excessive synchronized oscillatory activity in the beta frequency band (around 20Hz) in the basal ganglia and other parts of the brain. This review explores the dynamics and potential mechanisms of these oscillations employing ideas and methods from nonlinear dynamics. We present extensive experimental documentation of the relevance of synchronized oscillations to motor behavior in Parkinson's disease, and we discuss the intermittent character of this synchronization. The reader is introduced to novel time-series analysis techniques aimed at the detection of the fine temporal structure of intermittent phase locking observed in the brains of parkinsonian patients. Modeling studies of brain networks are reviewed, which may describe the observed intermittent synchrony, and we discuss what these studies reveal about brain dynamics in Parkinson's disease. The parkinsonian brain appears to exist on the boundary between phase-locked and nonsynchronous dynamics. Such a situation may be beneficial in the healthy state, as it may allow for easy formation and dissociation of transient patterns of synchronous activity which are required for normal motor behavior. Dopaminergic degeneration in Parkinson's disease may shift the brain networks closer to this boundary, which would still permit some motor behavior while accounting for the associated motor deficits. Understanding the mechanisms of the intermittent synchrony in Parkinson's disease is also important for biomedical engineering since efficient control strategies for suppression of pathological synchrony through deep brain stimulation require knowledge of the dynamics of the processes subjected to control.

Neural dynamics in parkinsonian brain: the boundary between synchronized and nonsynchronized dynamics

Synchronous oscillatory dynamics is frequently observed in the human brain. We analyze the fine temporal structure of phase-locking in a realistic network model and match it with the experimental data from Parkinsonian patients. We show that the experimentally observed intermittent synchrony can be generated just by moderately increased coupling strength in the basal ganglia circuits due to the lack of dopamine. Comparison of the experimental and modeling data suggest that brain activity in Parkinson's disease resides in the large boundary region between synchronized and nonsynchronized dynamics. Being on the edge of synchrony may allow for easy formation of transient neuronal assemblies.

Fine temporal structure of beta oscillations synchronization in subthalamic nucleus in Parkinson's disease

Synchronous oscillatory dynamics in the beta frequency band is a characteristic feature of neuronal activity of basal ganglia in Parkinson's disease and is hypothesized to be related to the disease's hypokinetic symptoms. This study explores the temporal structure of this synchronization during episodes of oscillatory beta-band activity. Phase synchronization (phase locking) between extracellular units and local field potentials (LFPs) from the subthalamic nucleus (STN) of parkinsonian patients is analyzed here at a high temporal resolution. We use methods of nonlinear dynamics theory to construct first-return maps for the phases of oscillations and quantify their dynamics. Synchronous episodes are interrupted by less synchronous episodes in an irregular yet structured manner. We estimate probabilities for different kinds of these "desynchronization events." There is a dominance of relatively frequent yet very brief desynchronization events with the most likely desynchronization lasting for about one cycle of oscillations. The chances of longer desynchronization events decrease with their duration. The observed synchronization may primarily reflect the relationship between synaptic input to STN and somatic/axonal output from STN at rest. The intermittent, transient character of synchrony even on very short time scales may reflect the possibility for the basal ganglia to carry out some informational function even in the parkinsonian state. The dominance of short desynchronization events suggests that even though the synchronization in parkinsonian basal ganglia is fragile enough to be frequently destabilized, it has the ability to reestablish itself very quickly.

Gamma knife stereotactic radiosurgery for low-grade astrocytomas

Patients with low-grade astrocytoma (LGA; 8 pilocytic astrocytomas, 2 subependymal giant cell astrocytomas, 2 fibrillary astrocytomas) were selected for treatment with gamma knife stereotactic radiosurgery (GKSRS) based on having a demarcated appearance on CT or MRI and the possibility of dose sparing of adjacent eloquent structures. A median dose of 13 Gy was prescribed to the 50% isodose line, which covered the gross tumor. The median patient age was 17.4 years. The median target volume was 4.4 cm(3). With a median follow-up of 48.2 months, 4-year tumor control and overall survival were 77 and 83%, respectively. Only 2 patients experienced symptomatic treatment-related toxicity. GKSRS can provide local control in cases of unresectable or recurrent LGA with a low incidence of side effects in carefully selected patients.

Endocrine response after gamma knife-based stereotactic radiosurgery for secretory pituitary adenoma

PURPOSE

To examine treatment outcomes of Gamma Knife-based stereotactic radiosurgery (GK-based SRS) for secretory pituitary adenomas.

MATERIALS AND METHODS

25 patients were treated with GK-based SRS for secretory pituitary adenomas with >or=12 months of follow-up.

RESULTS

For prolactinomas, 2 of 4 patients (50%) showed normalization of serum prolactin at a mean time of 18 months. One of 4 had a >or=50% decrease but still abnormal prolactin levels. For adrenocorticotrophic hormone-secreting tumors, 6 of 12 patients (50%) showed normalization of their endocrine levels at a median of 10 months. An additional 2 (17%) had a >or=50% decrease. For growth hormone-secreting tumors, 4 of 9 patients (44%) showed normalization of endocrine levels at a median time of 30 months. Two patients (22%) had >or=50% lower but abnormal endocrine levels.

CONCLUSION

GK-based SRS provides a reasonable rate of endocrine normalization of secretory pituitary adenoma. The time to endocrine response is shorter than reported for fractionated external beam radiotherapy. There is a low risk of optic neuropathy.

Gamma-knife-based stereotactic radiosurgery for uveal melanoma

Nineteen patients with uveal melanoma were treated with Gamma-Knife-based stereotactic radiosurgery (SRS). The radiation dose was 40 Gy prescribed to the 50% isodose line for all patients. The median follow-up was 40 months. The 3- and 5-year overall survival rates were 86 and 55%, respectively. The 3- and 5-year tumor control rates were both 94%. Six of the 19 treated patients (32%) developed distant metastasis 31-75 months after SRS. Out of the 19 patients treated with SRS, 2 had improved, 4 had stable and 13 had worse vision in the treated eye. Gamma-Knife-based SRS appears to provide excellent local control of uveal melanoma. The risk of distant metastasis is significant. Effective systemic therapy is to be explored to improve the treatment outcome of uveal melanoma.

Gamma Knife Radiosurgery in the Treatment of Choroidal Neovascularization (Wet-Type Macular Degeneration)

We evaluated retrospectively our institutional experience in the treatment of macular degeneration with gamma knife radiosurgery (GKR). Treatment was delivered in a single shot of 12 Gy. Seven patients were treated between March of 1999 and May of 2000. The median duration of follow-up was 2.2 years. The majority of patients maintained stable visual acuity after treatment. Our series indicates that GKR may be useful as a salvage treatment for patients who have failed or are ineligible for other treatments for their macular degeneration. Further studies are needed to better define the role of GKR in the treatment of macular degeneration.

The role of Gamma Knife Radiosurgery in the management of unresectable gross disease or gross residual disease after surgery in ependymoma

PURPOSE/OBJECTIVE

To evaluate the efficacy and the toxicity of Gamma Knife (GK)-based stereotactic radiosurgery (SRS) in the management of gross disease in ependymoma.

MATERIALS AND METHODS

Eight patients with 13 ependymomas were treated with GK-based SRS in our institution for gross disease. Five patients were treated for recurrent disease that developed after surgery and external beam radiotherapy (EBRT), two received SRS to the gross disease after surgery and EBRT, and one received SRS alone (in a 1.3 year old child). Median EBRT dose was 54.4 Gy (range 50-55.8 Gy). Median SRS dose was 14 Gy (range 12-20 Gy). Seven of eight (87.5%) patients had SRS to a single lesion and one of eight (12.5%) patients had treatment to six tumors in three different sessions.

RESULTS

The median follow up was 30.2 months (range 8-65.4 months). Out of the eight patients treated with SRS, six (75%) were alive, four (50%) were alive with no recurrence, two (25%) were alive with recurrence, and two (25%) died of recurrent disease. Both patients treated with SRS as a boost were alive and without recurrence. Out of the five patients who received SRS as salvage treatment, three (60%) were alive, two (40%) were alive without recurrence, two (40%) developed distant failure, and three (60%) had in-field control. Two patients who received SRS to their brainstem lesions developed symptoms related to radionecrosis and were successfully treated with steroid with good control of symptoms.

CONCLUSIONS

GK-based SRS appears to be a feasible and safe treatment modality for patients with ependymoma with unresectable gross disease or gross residual disease after surgery. SRS provides reasonable local control but out-of-field tumor progression remains an issue. For patients who receive SRS as a boost, the local control appears to be excellent.

Inguinal neurectomy for inguinal nerve entrapment: an experience with 100 patients

BACKGROUND

Inguinal nerve entrapment is a debilitating postoperative problem.

PATIENTS AND METHODS

One hundred patients were treated for inguinal nerve entrapment, including 52 men and 48 women with an average age of 45 +/- 14 years. Most patients had inguinal hernia repairs or Pfannenstiel incisions. Mesh was found in 27% of patients. Symptoms included pain (100%), radiation of pain to the thigh and/or genital area (59%), and postural pain (59%). Diagnosis was made by physical examination, postural maneuvering, and inguinal nerve block. Proximal nerve resection was followed by Mersiline (Ethicon, Inc., Somerville, NJ) ligature and absolute alcohol or phenol application to prevent neuromas.

RESULTS

Five percent of patients had minor complications. There was abnormal nerve histopathology in 18%. Total pain relief was attained in 72% of patients, partial relief in 25%, and no relief in 3%. Two patients complained of numbness postoperatively. Multifactorial analysis showed recurrent hernia repair as a significant predictive factor.

Failure of single-unit neuronal activity to differentiate globus pallidus internus and externus in Parkinson disease

OBJECT

The authors examine the validity of single-unit neuronal recordings as a method of differentiating the globus pallidus internus (GPi) from the GP externus (GPe) in Parkinson Disease.

METHODS

One hundred twenty-eight recordings of apparent single-unit activity used to help guide final electrode placement in eight patients who underwent pallidotomy were analyzed using sophisticated spike sorting methods, and 185 neurons were characterized for mean firing frequency and percent of firing within bursts. In addition, the total spectral power was calculated on the full measured waveform for each of 128 samples without spike sorting. No correlation was identified between these measures of neuronal activity and depth within the GP.

CONCLUSIONS

These results call into question the validity of relying on single-unit activity and microelectrode recordings in the operating room to localize lesion or electrode placement within the GPi during stereotactic pallidal surgery.

A coupled ordinary differential equation lattice model for the simulation of epileptic seizures

A coupled ordinary differential equation lattice model for the CA3 region of the hippocampus (a common location of the epileptic focus) is developed. This model consists of a hexagonal lattice of nodes, each describing a subnetwork consisting of a group of prototypical excitatory pyramidal cells and a group of prototypical inhibitory interneurons connected via on/off excitatory and inhibitory synapses. The nodes communicate using simple rules to simulate the diffusion of extracellular potassium. Both the integration time over which a node's trajectory is integrated before the diffusional event is allowed to occur and the level of inhibition in each node were found to be important parameters. Shorter integration times lead to total synchronization of the lattice (similar to synchronous neural activity occurring during a seizure) whereas longer times cause more random spatiotemporal behavior. Moderately diminished levels of inhibition lead to simple nodal oscillatory behavior. It is postulated that both the lack of inhibition and an alteration in conduction time may be necessary for the development of a behaviorally manifest seizure. (c) 1999 American Institute of Physics.

Leprosy in Hawaii; the end of an epidemic

Two different patterns of leprosy have occurred in Hawaii. First is the continuing influx of infected people among immigrants from several leprosy-endemic areas. The number of new cases among their descendents has tended to abate within one generation after arrival in Hawaii. The most recent example of this has occurred in Asians arriving since immigration laws were liberalized in 1965, followed by a rise of imported leprosy, peaking in 1970-1980, then falling. The second pattern was an explosive epidemic among native Hawaiians, rising to its peak in the 1890s, then slowly subsiding, and now approaching zero. It appears that official disease-control efforts (physical isolation and/or early multidrug treatment) cannot fully explain the ending of the epidemic in Hawaii, in spite of the continuing importation of M. leprae. It is suggested that the influence of changing socioeconomic factors (nutrition, crowding, genetics) has been of importance, particularly among the Hawaiians, who have undergone profound foreign influence (both positive and negative) during the 150-year history of this epidemic. The late Dr. Ma Haide was responsible for leprosy control in China, where leprosy is also fading away, but not simultaneously in all subpopulations. He summarized his view by saying, "Leprosy lingers longest among the poorest" (personal communication). This statement appears to hold true for Hawaii, also.

Medical insurance claims as a source of data for research: accuracy of diagnostic coding

Validation of diagnostic codes in a sample of Hawaii medical insurance claims in 1986 to 1987 revealed 96% accuracy in hospital claims, high enough to supply data for research purposes. In physician claims the accuracy was only 62%. Initiation of two feedback loops to physicians from the insurer in 1989 resulted in a marked improvement of diagnostic coding accuracy by 1992 to 1994.

Ictal brain imaging in presurgical evaluation of patients with medically intractable complex partial seizures

At the Indiana University Medical Center, 99 patients with medically intractable complex partial seizures (MI-CPS) had presurgical evaluation with subsequent anterior temporal lobectomy. The majority of the patients had single photon emission tomography (SPECT) performed interictally as well as during an actual epileptic seizure (ictal scan). Decreased regional cerebral perfusion (rCP) was seen in 54/94 (57%) of the interictal scans corresponding to the eventual site of the surgery. However, ictal scans provided a higher yield; increased rCP in the temporal lobe during an actual seizure was observed in 60/82 (73%) concordant to the side of surgery. SPECT is a useful, noninvasive method of localizing the epileptiform focus in patients with MI-CPS considered for resective surgery. Both interictal and ictal SPECT need to be performed; combined interictal hypoperfusion and ictal hyperperfusion in the same focal area are unique to epileptogenic lesions. Ictal SPECT studies can be performed in the majority of patients during the period of continuous video/EEG monitoring with only a little additional effort. Combining the results of functional brain imaging (interictal and ictal SPECT, PET) with clinical semiology of seizures, surface and sphenoidal EEG, magnetic resonance imaging and other non-invasive tests, anterior temporal lobectomy can be recommended in approximately two-thirds of the patients without resorting to potentially dangerous intracranial EEG monitoring.

Suprascapular nerve entrapment. A series of 27 cases

Suprascapular nerve entrapment is an acquired neuropathy secondary to compression of the nerve in the bony suprascapular notch. A series of 27 cases, the largest reported to date, is presented and examined as to the best and most appropriate method of diagnosis and treatment. The entity is described in detail as to its origin, anatomy, and pathophysiology.

Contemporary management of neurofibromatosis

The neurofibromatoses are two distinct entities with different genetic origins. The phenotypic expressions and required treatments are different. The devastating nature of neurofibromatosis-2 may be more effectively controlled through the application of advanced imaging techniques and contemporary neurotologic procedures. The most common manifestation of neurofibromatosis-2 is that of bilateral acoustic neuromas. The eventual total bilateral sensorineural deafness associated with this condition can be obviated in selected cases if the diagnosis is established early. Follow-up data are reported for three patients in whom hearing was preserved in at least one ear. When removal with hearing preservation is not possible, subtotal tumor removal with decompression of the internal auditory canals may delay progression of hearing loss. A new approach to tumors of the pterygomaxillary fossa that have extended to the middle cranial fossa has been successfully applied and is described.

HIPDM-SPECT brain imaging in the presurgical evaluation of patients with intractable seizures

We report the results of interictal and ictal HIPDM-SPECT brain imaging in 34 patients who eventually underwent temporal lobectomy for treatment of medically intractable complex partial seizures. Interictal studies revealed decreased regional cerebral perfusion (rCP) in the temporal lobe corresponding to the eventual site of surgery in 73% of the patients. Similarly, ictal study demonstrated increased rCP in 93% of the patients. In 69% of the patients, the SPECT studies were able to demonstrate both increased rCP on the ictal scan and decreased rCP on the interictal scan in the same location, corresponding to the eventual site of surgery. These results suggest that interictal and ictal SPECT brain imaging can be easily obtained and provide reliable localizing information in the presurgical evaluation of patients with medically intractable epilepsy.

Hereditary amyloidosis: evidence against early amyloid deposition

Twelve members of the Indiana hereditary amyloidosis type II kindred were tested for the presence of amyloid deposits. All were young adults (age 26-37), with no evidence of disease and with 1 affected parent. Six were found to be carriers of the variant gene, by DNA testing and/or reduced serum retinol-binding protein levels. Nevertheless, no amyloid could be found in any skin, rectal, or carpal tunnel biopsy specimens. Our results suggest that hereditary amyloidosis type II is a true late-onset disease, in which accumulation of amyloid does not start until late in life--perhaps only a short time before symptoms appear.

Intramedullary spinal Histoplasma granuloma. Case report

While there have been several cases of cerebral histoplasmoma published in the literature, the occurrence of such a lesion in an intramedullary spinal location has not previously been reported. The authors present a patient with a Brown-Séquard lesion secondary to an intramedullary Histoplasma granuloma in the cervical region. The case was successfully managed with surgical removal of the lesion.

HIPDM-SPECT in patients with medically intractable complex partial seizures. Ictal study

Both interictal and ictal N,N,N'-trimethyl-N'-(2-hydroxy-3-methyl-5-iodobenzyl)-1,3,propanediamine -single photon emission computed tomography (HIPDM-SPECT) were performed in 16 patients with medically intractable complex partial seizures. Ictal HIPDM-SPECT localized epileptic foci in 13 of 14 patients with unilateral temporal focus and provided confirmative evidence of epileptic focus in 11 patients by demonstrating maximally increased regional cerebral perfusion (rCP) in epileptic foci that had shown decreased rCP in a previous interictal study. Ictal HIPDM-SPECT in two patients with bitemporal foci showed more complicated patterns consisting of slightly increased rCP in bilateral multifocal regions. Ictal HIPDM-SPECT was particularly useful for investigating epileptic foci, and correlation with simultaneously recorded ictal electroencephalograms provided further insight for localizing epileptic foci.

Single photon emission computed tomography (SPECT) brain imaging using N,N,N'-trimethyl-N'-(2 hydroxy-3-methyl-5-123I-iodobenzyl)-1,3-propanediamine 2 HCl (HIPDM): intractable complex partial seizures

HIPDM-SPECT brain imaging was performed in four patients with intractable complex partial seizures (CPS). Three patients had an epileptogenic focus in one temporal lobe and underwent anterior temporal lobectomy. Interictal HIPDM-SPECT demonstrated decreased regional cerebral perfusion (rCP) in the epileptogenic area in only one patient, but ictal studies showed increased rCP in the epileptic foci of all three patients. In the fourth patient, interictal HIPDM-SPECT showed increased rCP in the area of epileptogenic focus; when antiepileptic medication was taken, rCP decreased. HIPDM-SPECT brain imaging is useful for localizing epileptogenic foci in CPS.

Measuring clinical performance of individual internists in office and hospital practice

No standardized methods exist for reliably measuring physicians' performance against clinically valid standards. In this study, statistically reliable peer review based on current national standards of internal medicine was used to evaluate the clinical performance of 66 internists in office and hospital practice. Evaluation was limited to the substantiation of diagnosis, prescribing indicated drug regimen, monitoring, and attaining expected patient response. Performance in substantiating diagnosis was better than in therapeutic management, and management in hospitalized patients was superior to office management. Superior performance by a physician was not consistent across diagnoses, but substandard office treatment in at least one diagnosis was associated with substandard office treatment in other conditions. Internists' performance was unrelated to their certification status but inversely related to the number of years since graduation from medical school. This method could be used to evaluate the effectiveness of continuing education in improving physicians' performance and to validate current examinations used in recertifying internists.

Field evaluation of an ELISA to detect antibody in leprosy patients and their contacts

Previous studies have detected circulating antibody in leprosy using a variety of difficult laboratory methods. We have developed a simpler method for detecting antibody by ELISA, using autoclaved Mycobacterium smegmatis as the antigen. Evaluation was performed on eluates from 25 microliter aliquots of finger-prick blood dried on filter-paper disks in two high-incidence populations in Ponape, Micronesia. Among 228 nonleprosy cases bled in 1980 and rebled and re-examined in 1982: a) for those who had been ELISA positive two years earlier, the leprosy attack rate during the intervening two years was at least twice as high as among those who had been negative, and we estimate that shortening the screening interval to one year plus doing confirmatory retests on new sero-converters would increase the relative risk (or "predictive power") to over sixfold, including all impending multibacillary cases; b) elevated antibody levels were detected up to two years prior to clinical onset of disease in 70% of new cases; and c) both asymptomatic conversion (rising titer) and reversion (falling titer) were observed. Among 150 biopsy-proven cases, ELISA results suggest that fall of titer in most uncomplicated paucibacillary cases was rapid (months), but in multibacillary cases was more gradual (years), probably paralleling responses to treatment with titers rising in reactivation. These results suggest that this technique, with an improved antigen, may be useful in leprosy control programs, both for detecting candidates for preventive treatment and for following responses to therapy.

Saphenous nerve entrapment. A cause of medial knee pain

Saphenous nerve entrapment is a seldom recognized cause of pain along the medial side of the knee and proximal calf. We are reporting our experience with 15 saphenous nerve entrapments in 14 patients between 1978 and 1981.

Spontaneous saphenous neuralgia

Six patients representing seven cases of spontaneous (nontraumatic) saphenous neuralgia secondary to entrapment of the nerve in the subsartorial canal are presented. All patients complained of medial knee and leg pain. Clinical findings included tenderness over the subsartorial canal and sensory changes in the cutaneous distribution of one or both terminal branches of the saphenous nerve. The diagnosis was confirmed by saphenous nerve block in all cases. All patients were treated operatively, which resulted in symptomatic improvement. All six patients initially underwent external neurolysis; however, three patients required saphenous neurectomy for recurrent symptoms. Saphenous neuralgia should be considered in the differential diagnosis of medial lower extremity pain.

Dependence of batrachotoxin block of axoplasmic transport on sodium

Batrachotoxin (BTX) in the low concentration range of 19-190 nM blocks axoplasmic transport in the desheathed cat peroneal nerve in vitro. When the level of Na+ in the incubation medium was reduced to 10 mM, the blocking effect of BTX was much diminished, and in an Na+-free medium BTX had no effect on transport at all. The blocking action of BTX with Na+ present was inhibited by increasing the concentration of Ca2+ in the experimental medium. Relatively small increases were effective with a maximum protection seen when the Ca2+ concentrations were 7-10 mM. The results support the view that an increase in axonal Na+ is inhibitory to the transport mechanism. The results are discussed on the basis of the recently developed transport filament model of axoplasmic transport which takes into account an obligatory role for Ca2+ in transport and its axonal regulation. The possible relation of intraaxonal Na+ concentration to the Ca2+ level is also discussed.

Utilization and cost effectiveness of a family practice center

In a prepaid group practice setting, a group of 45 Family Practice Center patients, carefully matched by age, sex, and employment, were compared with a group of 63 patients attending medical and pediatric clinics. Utilization rates for physician and nonphysician visits and costs of laboratory and x-ray services during a period of 33 months were examined. Despite a 25 percent greater prevalence of significant chronic medical problems, the family practice group used specialist care less than one half as much as did the matching group and made one extra physician visit per patient per year. Costs for laboratory and x-ray procedures did not differ significantly. Satisfaction expressed in responses to telephone interviews of both groups was found to be somewhat greater among the family practice patients. The findings of this study provide some support for greater cost effectiveness and patient satisfaction of family practice compared with alternative modes of primary care.

Immigration and leprosy in Hawaii, 1960-1981

The 140-year-old epidemic of leprosy among the people of Hawaii reached its peak at about the beginning of this century and has been subsiding ever since. A preliminary review of new cases in Hawaii in the past 15 years showed 49 among those born in Hawaii, plus 360 new immigrant cases (largely from the Philippines and Samoa), 130 of whom were of the borderline lepromatous or lepromatous (BL/L) form. Since 1970 all new cases have been treated as ambulatory patients in their home communities. A detailed review of all 95 new Hawaii-born cases in the past 21 years showed a continuing rapid decline in incidence among ethnic Hawaiian people, with a fall in the proportion of BL/L cases from its former plateau around 40% to only 20% in the last seven years. The new immigrant BL/L cases have apparently not caused a significant secondary outbreak among the Hawaiians but have caused a modest increase among groups. Among these recent non-Hawaiian secondary cases, the proportion of BL/L cases has also recently dropped so sharply that the risk of significant tertiary spread is minor. The possible role of improved nutrition in Hawaii as an influence on these recent leprosy patterns is suggested.

Brain stem auditory, visual and somatosensory evoked potentials in leukodystrophies

Brain stem auditory (BAERs), visual (VEPs) and somatosensory evoked responses (SEPs) were recorded in 12 patients with Pelizaeus-Merzbacher leukodystrophy (PMD), three with adrenoleukodystrophy (ALD) and three with metachromatic leukodystrophy (MLD). All the 3 evoked responses were abnormal in all patients except normal VEPs and SEPs in a patient with early ALD. In most patients wave I with and without wave II were the only components of the BAERs that remained, subsequent components (waves III-VII) were absent. VEPs were severely altered; either no identifiable response to flash or pattern reversal stimuli could be recorded or the major components were significantly delayed in latency. Short latency SEPs following median nerve stimulation usually showed a normally recorded Erb's potential (N10), but an absence or marked attenuation of cervical (N14) and early scalp components (N19 and P22) or the occurrence of the scalp components with a significant delay. Multimodality evoked responses provide more information regarding the functional integrity of several afferent systems in patients with white matter disorders.

Evoked responses in the diagnosis of thoracic outlet syndrome

The lack of an objective method for diagnosing thoracic outlet syndrome and monitoring the results of treatment has prevented a clear understanding of its natural history and the indications for surgery. Although one can detect vascular compression, the majority of patients have symptoms that are primarily neurogenic; and neither electromyograms nor studies of nerve conduction velocity has proved consistently helpful in their evaluation. We have studied evoked responses in 22 patients and believe that this technique allows selection of patients with significant neural compression for operative treatment. In this procedure, a bipolar stimulating electrode is placed on the median and ulnar nerves at the wrist; and bipolar recording is performed from active electrodes placed at Erb's point, over the spines of C6 and C2, and over the contralateral parietal scalp, all referenced to a midfrontal electrode. A minicomputer temporally summates the low-amplitude potentials elicited by repetitive electrical stimulation to increase the signal to noise ratio and therefore distinguish the potentials of interest from the background bioelectric activity. Normative values have been determined, allowing detection of changes in conduction of the electrical activity that occur between the sites of stimulation and the sites of recording. Of 19 new patients, 13 had abnormal evoked responses. Nine of these underwent surgical treatment; eight obtained good or excellent results. Abnormalities in evoked responses disappeared after operation in seven of the eight in whom it was measured. Four patients with abnormal responses but no surgery are being evaluated. Two of three long-term patients with recurrent symptoms had abnormal evoked responses that changed after treatment. Longer follow-up is needed to determine if this method is helpful in selecting patients for operative treatment or in monitoring its results.

The requirement for calcium ions and the effect of other ions on axoplasmic transport in mammalian nerve

1. Until recently it was believed that axoplasmic transport in vitro was not affected by Ca2+, transport being normal in Ca2+-free medium. This was found due to the presence of the relatively impermeable perineurial sheath around the nerve trunks. Using a desheathed cat peroneal nerve preparation, axoplasmic transport was shown to require an adequate level of Ca2+ in the external medium. In a buffered Ca2+-free medium, transport began to decline within 30 min and a complete block occurred in 2 . 6 hr. A concentration of 5 mM-Ca2+ added to a buffered isotonic sucrose of NaCl solution was able to maintain transport. With lower concentrations of Ca2+ of 1 . 5-3 . 0 mM, those usually present in the extracellular fluid or in a Ringer medium, some impairment of transport was seen but the addition of 4 mM-K+ restored the normal pattern of axoplasmic transport. With Ca2+ concentrations below 0 . 75 mM, however, 4 mM-K+ was unable to sustain transport. 2. Potassium by itself at a concentration of 4 mM when added to a buffered isotonic sucrose of NaCl medium was unable to prolong the time of transport block beyond that seen in buffered isotonic NaCl or sucrose solutions. In concentrations of K+ up to 25 mM, 1 . 5-5 mM-Ca2+ was required for normal transport. With moderately higher concentrations of K+ in the range of 50-100 mM, normal appearing transport was seen with or without Ca2+. This was seen whether or not Na+ was present in the medium. At higher levels of K+, 120-150 mM, decreased transport was seen, with or without the addition of either 15 mM-Na+ or Ca2+ in concentrations of 1 . 5-3 . 0 mM. 3. While Mg2+ could not substitute completely for Ca2+ in maintaining transport, it was able to prolong the time before block occurred. An extra 30-60 min of downflow was seen when 5 mM-Mg2+ was added to a buffered isotonic NaCl medium. Magnesium also acts synergistically with Ca2+. Concentration of Ca2+ as low as 0 . 25 mM was, with the addition of 1 . 5 mM-Mg2+, able to maintain transport. 4. The results are interpreted in the light of studies of the mechanism of Ca2+ regulation known to occur in giant nerve fibres and other clls controlling the level of free Ca2+. The relationship of Ca2+ to the mechanism considered to underlie axoplasmic transport in nerve fibres is also discussed.