An Exploratory Study of Field Failures

Field failures, that is, failures caused by faults that escape the testing phase leading to failures in the field, are unavoidable. Improving verification and validation activities before deployment can identify and timely remove many but not all faults, and users may still experience a number of annoying problems while using their software systems. This paper investigates the nature of field failures, to understand to what extent further improving in-house verification and validation activities can reduce the number of failures in the field, and frames the need of new approaches that operate in the field. We report the results of the analysis of the bug reports of five applications belonging to three different ecosystems, propose a taxonomy of field failures, and discuss the reasons why failures belonging to the identified classes cannot be detected at design time but shall be addressed at runtime. We observe that many faults (70%) are intrinsically hard to detect at design-time

Callosotomy

Corpus callosotomy is a reasonably safe and effective palliative surgical procedure for some patients with intractable seizures who are not amenable to focal resection, it does not pretend to suppress seizures, but it aims at alleviating them, by reducing their severity [13, 14, 15]. This is a feasible and costeffective treatment for some patients, even those in developing countries and with limited resources [19]. It is useful for seizure control in adult and in children, particularly in children with catastrophic epilepsy syndromes. Lennox-Gastaut syndrome is the most common one and the result of seizure control is significant. Severe mental retardation is not a contraindication to perform callosotomy. As a reguard seizure type generalized seizures with fall (Drop-Attack) are the most responsive to callosotomy. Seizure control , when obtained, is stable over time [13]. Improved seizure control after callostomy is always associated with improved QOL, satisfaction of parents to the operation, and also satisfaction of family QOL. Significant neuropsychological deficits are evident only on formal testing, are usually ignored by patients/family members, and rarely cause impact on daily life

La stimolazione vagale

La maggior parte degli Autori \ue8 concorde nel ritenere che la risposta clinica alla VNS sia migliore in et\ue0 pediatrica rispetto all\u2019et\ue0 adulta, il cut off viene posto a 18 anni, la significativit\ue0 statistica aumenta se vengono presi in considerazione i bambini impiantati ad una et\ue0 inferiore ai 6 anni . L\u2019et\ue0 all\u2019impianto \ue8 strettamente correlata con la durata dell\u2019epilessia poich\ue8 la maggior parte dei soggetti trattati ha presentato un esordio critico entro i primi anni di vita. I dati della letteratura riferiti ai soggetti adulti sembrano indicare che i pazienti affetti da crisi parziali complesse con alterazioni parossistiche focali/multifocali con o senza bisincronismo secondario siano candidati ad una risposta ottimale al trattamento. I soggetti affetti da sindrome di Lennox Gastaut e crisi di caduta atonica sembrano essere i pi\uf9 resistenti. Altri fattori quali l\u2019eziologia, il numero di crisi pre-impianto, l\u2019entit\ue0 del ritardo mentale, il numero di farmaci non sembrano influire significativamente sulla risposta clinica

Interictal epileptic activity during sleep: a stereo-EEG study in patients with partial epilepsy

Cerebral electrical activity was recorded through chronic stereotactically implanted electrodes in 19 epileptic patients suffering from different types of severe and medically refractory partial seizures and who were considered for surgical treatment. 213 brain sites, in all cerebral lobes, in neocortical as well as in archicortical structures, were explored. The behaviour of the interictal spiking across wakefulness and nocturnal physiological sleep was analysed, using automatic elaboration. (i) Spike rate is affected by the occurrence of sleep and by the passage from one sleep phase to another. The degree and direction of the phenomenon differ remarkably in the various patients and, in the same patient, in the different cerebral sites explored. Generally, interictal spiking increases at the beginning of sleep, reaches its maximum during the deep non-REM phases and returns to a level slightly lower than that in wakefulness during REM. (ii) The nocturnal spike rate is hardly influenced by spike location. In most cases, however, the variations recorded during sleep are more significant in the frontal regions than elsewhere. (iii) Spike rate across wakefulness and sleep is affected by the local level of epileptogenicity: spiking variations are less in the most epileptogenic cerebral zone (identified by the origin of the seizure discharges and by the disappearance of seizures following its surgical removal) than elsewhere. The physio-pathological meaning and the diagnostic value of these findings, and particularly of the peculiar stability or autonomy of the electrical epileptic activity of the most epileptogenic cerebral zone, is discussed

Resection surgery for partial epilepsy. Relation of surgical outcome with some aspects of the epileptogenic process and surgical approach

In spite of the progressive improvement of the results of resective surgery for epilepsy, the number of not significantly benefited patients remains high. An attempt was made to find out a relation between outcome and some aspects of the pathophysiological organization of the epileptogenic process and of the surgical procedure. Chi-square and logistic regression statistic analyses were utilized. The study was retrospectively performed on 138 surgically treated patients having a minimum follow-up of three years. Three classes of surgical outcome were considered: completely seizure free (including aura; 86 cases, 62.3%), significant seizure reduction (31 cases, 22.5%), and no significant improvement (21 cases, 15.2%). What follows was brought into evidence by the study. 1) On the diagnostic side, the spatial arrangement (focal, unilateral, multifocal) of both the interictal and the ictal epileptic electrocerebral activities are significantly associated with the surgical outcome. Their relative impact on outcome is related to the presence of a structural lesion: when a lesion is documented, the interictal activity has the higher value: vice versa, when no lesion is apparent, the role of the ictal activity is prevalent. However, the presence, as well as the nature of the lesion, per se, are not significantly associated with outcome. 2) On the surgical side, the extent of resection of both the structural lesion and of the epileptogenic zone are highly associated with the surgical result; the extent of lesion resection prevails on that of the epileptogenic zone. The type of surgical approach (hemispherectomy: 17 cases; temporal lobectomy: 67 cases; extratemporal resection: 54 cases) has no significant relation to the outcome. The value and the limits of the results obtained are discussed

[Research on the epileptogenic complex]

The great importance of a correct definition of the lesional-functional epileptogenic complex for the surgical treatment of the epileptic patient is stressed. The means utilizable to reach the knowledge of the topographic organizatif the latters are descri0ed and discussed in detail: the scalp EEG, the examinations based on the EEG effects of endocarotid injection of barbiturates and convulsants, the EEG during nocturnal sleep, the direct recording of electrocerebral activity from the cortical surface (electro-corticography) and from deep cerebral structures (stereoelectro-encephalography). The relative importance of the informations provided by the electrical activity of "lesional" type, by the interictal epileptic activity and by the ictal one is analyzed. The utilization of methodologies of automatic elaboration of the electrocerebral signals is reminded. Finally, the different modes of application of the means of analysis mentioned above in the different epileptic patients are discussed and exemplified

[Usefulness of the stereo-electroencephalographic chronic exploration in epilepsy]

Tra le molteplici espressioni elettroencefalografiche che si riscontrano in forma intercritica o critica nei pazienti epilettici, frequentemente ritroviamo sia anormalità ricorrenti in modo sporadico, apparentemente occasionale, ed a distribuzione topografica variabile, sia fenomeni stabili nel tempo e nella loro topografia

Discussion on the causes of failure of surgical treatment of partial epilepsies

Despite continuous improvement in diagnosis and surgery, persistence of seizures following surgical treatment of partial epilepsies still occurs in a relevant number of cases (30--40%). The analysis of personal material and of data from the literature appears to indicate that relevant causes of surgical failure are difficulties in delimitation of the epileptogenic zone and therefore of complete surgical removal. These difficulties are illustrated and discussed

Short and middle-latency Median Nerve (MN) SEPs recorded by depth electrodes in human pre-SMA and SMA-proper

OBJECTIVE: To analyse waveforms, latencies and amplitudes of Median Nerve (MN) SEPs recorded by stereotactically electrodes implanted in the SMA of 14 epileptic patients (9 in pre-SMA,3 in SMA-proper, 2 in both) in order to evaluate which short and middle-latency SEPs are generated in this area and which could be the physiological relevance of these responses. METHODS: Short and middle-latency MN SEPs were recorded by chronically implanted electrodes in the fronto-temporal cortex and in particular in the mesial frontal region of 14 drug-resistant epileptic patients. MN stimulations of 100 micros were delivered by skin electrodes at the wrist; stimulus intensity was adjusted slightly above the motor threshold. RESULTS: The main result of this study is that middle-latency SEPs were originated in pre-SMA but not in SMA-proper as demonstrated by both referential and bipolar recordings. In particular off-line computed bipolar traces between neighbouring contacts implanted in the pre-SMA and in the frontal external regions showed a phase reversal at the deepest contacts located in pre-SMA. Conversely, bipolar recordings between neighbouring contacts implanted in the SMA-proper and in the frontal external regions showed inversion recovery at more superficial contacts, implanted in area 6. Finally, we confirmed that no short-latency MN SEP (and in particular the N30) is originated in the whole SMA. CONCLUSIONS: Among premotor areas, somatosensory inputs seem to reach pre-SMA and area 6 but not SMA-proper. SIGNIFICANCE: This study assessed that no scalp SEP in the first 100 ms after MN stimulus could be generated in SMA-proper

Sleep and epileptic activity

Thirteen patients suffering from severe partial epilepsy and potential candidates for surgical treatment were investigated with stereotactically implanted intracerebral electrodes during nocturnal physiological sleep. The recorded electrocerebral activity was automatically analyzed to gain information on interictal epileptic events during wakefulness and the phases of sleep. The interictal epileptic activity shows: (1) great variability in the different subjects, and intra-individually, variability according to the explored cerebral regions; (2) is not influenced by the location of the recorded epileptic events; and (3) is affected by the local level of epileptogenicity. The latter was determined by the assessment of the capacity to give origin to ictal discharges and the disappearance of seizures following surgical removal. The interictal rate of spiking from the most epileptogenic cerebral zone is characterized by a relative stability during the night and by a relatively high degree during REM sleep