Diffusion tensor tracking of callosal fibers several years after callosotomy.

Diffusion tensor imaging (DTI) can provide more detailed in vivo information on the structural preservation of transected white matter tracts than conventional imaging methods. Here we show for the first time tracks of severed callosal fibers up to 17 years from resection. Five patients subjected to complete or partial callosotomy several years before the study were examined with DTI and compared to a normal control. Transected fibers were traced in all patients and were more clearly visible in the anterior and posterior parts than in the middle of the commissure. These findings suggest that microstructural changes persist for many years in the severed fibers, as also reflected by fractional anisotropy and apparent diffusion coefficient values, enabling a reconstruction of the longitudinal organization of severed central tracts that could not be achieved with previous techniques.

Review of corpus callosum topography, analysis of diffusion values for the different callosal fibers and sex differences.

Conventional MRI shows the morphology of the corpus callosum (CC), but does not reveal cortical connectivity or structural information on the CC. Here, we applied diffusion tensor imaging (DTI) in conjunction with a tract-tracing algorithm to incorporate cortical connectivity information on the CC in 40 subjects and to detect the main area and sex structural differences. CC parcellation was based on trajectories to different cortical (prefrontal, frontal motor/premotor/supplementary motor connections, parieto-occipital, temporal) and sub-cortical areas (capsular/basal ganglia connections). In agreement with recent DTI studies, we found that motor fibers occupy a much larger portion of the CC than previously believed on the basis of anatomical data. Differences in anisotropy values were instead in agreement with previous morphological evidence of smaller fibers in the anterior and posterior portions of the CC. The main sex difference was observed in anisotropy values in frontal fibers that proved to be lower in females than in males. Statistically significant differences in the regional diffusion parameters and between sexes give rise to many important questions regarding fiber organization patterns, CC microstructure and the functional relevance of these differences and provide evidence for the role of DTI, which reaches beyond the information given by morphological analysis.

Congenital dacryocystocele: diagnosis and treatment.

Five children were diagnosed with congenital dacryocystocele; in all cases, the cystic lesion was unilateral; age ranged from 7 to 60 days (mean 29 days). The mean ultrasonography diameter of the cyst, at the time of the diagnosis, was 11.51 mm. Topical and systemic antibiotics and massage were prescribed. One patient had no recurrence of the dacryocystocele but 4 showed no improvement with medical treatment; they were submitted to successful probing in the first months of life under general anaesthesia. Nasal endoscopy revealed a nasolacrimal cyst in one patient. True dacryocystocele is relatively rare: ultrasound is a simple, non-invasive method that can reliably distinguish dacryocystocele from other pathological conditions. Several reports have described a variable natural course of these lesions but there are controversial opinions regarding their management. Initially, we treated this congenital anomaly with digital massage, and topical and systemic antibiotics. Probing under general anaesthesia was performed in the event of dacryocystitis or lack of resolution after a short trial period with digital massage. Particular attention was paid to nasal bilateral endoscopy to exclude a nasal obstruction caused by cystic swelling of the nasolacrimal duct. When performed, the probing procedure was successful in all patients.

Control of inflammation and prophylaxis of endophthalmitis after cataract surgery: a multicenter study.

PURPOSE: To compare two different postcataract surgery antibiotic/steroid therapeutic combinations, for clinical results as well as patient satisfaction. METHODS: Prospective randomized clinical trial of patients with bilateral operative cataract. Postoperatively, for 15 days one eye was randomly assigned to therapy with the combination chloramphenicol 0.25%-betamethasone 0.13% gel three times a day (Group 1) and the other to the combination tobramycin 0.3%-dexamethasone 0.1% eyedrops four times a day (Group 2). RESULTS: A total of 142 patients (284 eyes) completed the study. The authors could not detect any significant difference between Group 1 and Group 2 concerning preoperative evaluation, surgical procedure, and complications. Pertaining to the two therapeutic regimens, efficacy, side effects, and clinical findings such as uncorrected visual acuity, intraocular pressure, edema or hyperemia of eyelids and/or conjunctiva, conjunctival and/or ciliary vessels congestion, decreased corneal transparency, corneal edema, Descemet folds, anterior chamber Tyndall and depth, and posterior synechiae were also comparable. Postoperative subjective pain and dry eye sensation were comparable between the two groups, while the gel preparation elicited a significantly more pleasant sensation in the patients (p=0.04). CONCLUSIONS: The motivation for use of a gel is to prolong the permanence of associated drugs on the ocular surface, increasing potency and decreasing concentration of the drug and rate of administration. This in order to improve compliance and decrease potential side effects. Chloramphenicol 0.25%-betamethasone 0.13% gel combination proved to have comparable efficacy, tolerance, and better acceptance by the patients than an aqueous tobramycin 0.3%-dexamethasone 0.1% preparation.

Two anomalous localizations of mucocele: clinical presentation and retrospective review.

Two Caucasian males (57 and 70 years old) were referred to our attention with parasinus mucoceles, maxillary and frontal mucocele, respectively, that had eroded the orbital rim and caused swelling of the eyelids and brow. Invasion of the orbital space caused several ophthalmic symptoms such as diplopia, proptosis, ptosis, and the formation of a palpable mass. Ophthalmic involvement was the first sign of the mucocele. The mucoceles were completely excised through a skin incision and the diseased mucosa of the sinuses was removed: endonasal fibre optic surgery and the Caldwell-Luc procedure were used in the patient with maxillary mucocele. The cases are described with retrospective review.

Suggestive evidence for an involvement of the right hemisphere in the recovery from childhood aphasia: a 3-year follow-up case study.

We describe the case of an 11-year-old, previously healthy, pre-puberal, right-handed girl with acquired aphasia following an extensive cerebral hemorrhage into a left hemisphere brain tumor. A 3-year follow-up evaluation of the girl's communicative performance showed an incomplete recovery of linguistic abilities with a good recovery of comprehensive components, but persisting severe impairment in expressive language. At the end of the follow-up period, with the aim of assessing the lateralization of some linguistic abilities, we carried out an experimental investigation using tachistoscopic reading and object naming tests along with a dichotic listening test. All these tests showed a clear left field/left ear-right hemisphere advantage. We discuss both clinical and experimental results with regard to implications for the linguistic abilities of the right hemisphere in late versus early childhood and its interaction with aetiology in the recovery from acquired childhood aphasia.

Stroop effects from 3 to 10 years: the critical role of reading acquisition.

We studied 241 nursery and primary school 3- to 10-year old children with a discrete-trial version of the Stroop Test, including both a Color-Naming and (for the 6- to 10-year olds only) a Word-Reading task. The classic Stroop effect was present across all the ages, with an inverted U-shaped pattern: increasing from 3- to 7-year olds, then decreasing. Preschool children who were able to read showed a Stroop effect larger than same-age, unable to read children. The reverse Stroop effect was present across all the studied ages but the 6-year-olds, who instead displayed some facilitation in reading congruent vs. black words. Since the acquisition of reading skills turned out to be crucial for the Stroop effects, the present research may be useful to study developmental reading impairments by providing normative data.

Iatrogenic Horner's syndrome.

PURPOSE: To report two cases of Horner's syndrome. One presented after the ablation of a schwannoma of the cervical sympathetic chain, the second after upper thorascopic sympathectomy for primary palmar hyperhidrosis. METHODS: A 42-year-old man underwent excision of a left neck mass found during routine physical examination. A 20-year-old girl with axillary and palmar hyperhidrosis was treated with cervical sympathectomy. RESULTS: In the early postoperative days, miosis, ptosis, anhidrosis, and enophthalmos were observed. CONCLUSIONS: In the ablation of a schwannoma, postoperative Horner's syndrome is associated with the relationship between nerves and the tumor mass, which makes it impossible to separate them surgically in most cases. In thorascopic sympathectomy, patients should be warned of this complication.

Efficacy and safety of bimatoprost in patients with uncontrolled glaucoma as alternative to filtration surgery.

PURPOSE: To evaluate the efficacy and safety of bimatoprost 0.03% as an alternative to filtration surgery in patients with uncontrolled glaucoma. DESIGN: Interventional study. METHODS: A total of 83 consecutive patients (83 eyes) awaiting glaucoma surgery were enrolled in eight ophthalmic centers. Reasons for listing were inadequate intraocular pressure (IOP) control despite medical therapy and documented progression of visual field loss. All patients discontinued the previous treatment and were switched to bimatoprost 0.03% QD (one drop at 9 pm). The primary efficacy outcome was a 20% IOP reduction from baseline at each timepoint. IOP was measured at day 7, day 30, day 60, and day 90 of treatment; less than 20% IOP reduction was considered as a failure. RESULTS: An IOP reduction of at least 20% was achieved in 74 patients (89.1%) after 7 days and in 64 patients (86.5%) after 30 days. Sixty-two patients (74.6%) maintained IOP readings 20% lower than baseline after 60 and 90 days. In these patients, visual field indices improved in 8 eyes (13%), and remained unchanged in 54 eyes (87%). Ocular side effects were conjunctival injection (15.6%), burning sensation (9.6%), foreign body sensation (4.8%), and eyelash growth (2.4%). CONCLUSIONS: This preliminary study shows that bimatoprost 0.03% could represent a useful therapeutic tool that might defer filtration surgery.

The contribution of general and specific motor inhibitory sets to the so-called auditory inhibition of return.

The detection of sounds that come from a region of space recently exposed to acoustic stimulation is often slower than the detection of sounds coming from regions of space previously unexposed to acoustic stimulation. The relative increase in reaction time (RT) to targets in recently stimulated locations is generally termed "inhibition of return" (IOR). This term alludes to the possibility that spatial attention is biased against returning to recently visited locations, thus favoring the sampling of new sources of information. However, auditory IOR effects found in paradigms where subjects have to detect a first sound (cue) without making an overt response to it, and then respond as fast as possible to a second sound (target), may be due to a purely motor inhibition carried over from cue to target. Such motor inhibition has been shown to be maximal when cue and target belong to the same category, such as when they occupy the same spatial position. We have assessed the possible contribution of this motor inhibition to auditory IOR effects by having subjects respond to both cues and targets randomly presented in a right location and a left location. Reaction time to targets preceded by cues at the same location was longer than reaction times to targets preceded by cues at the opposite location (IOR effect). Compared to a condition in which subjects responded only to targets, the IOR effect was smaller, but still significant, in the double response condition, suggesting that such an effect depends on both motor inhibition and other factors, possibly related to covert spatial orienting and oculomotor control. A second experiment indicated that the IOR effect component independent of motor inhibition was slightly but significantly greater when space was relevant to the task because subjects had to report the positions of both cues and targets, compared to when space was irrelevant to the task because subjects were not required to report stimulus positions.

Taste laterality in the split brain.

Two patients with corpus callosum resection, one complete and the other sparing the genu and the rostrum, were tested for discrimination of three basic taste stimuli (sour, bitter, salty) applied to the right or left sides of the tongue. Responses were made by pointing with either hand to written words or images of visual objects corresponding to the stimuli, a language-based discrimination. In both patients, response accuracy was significantly above chance for both hemitongues but there was a significant advantage for the left side. Reaction time was shorter for left stimuli than for right stimuli but the difference was not significant. Eight normal controls matched for age with the patients performed equally well with right and left hemitongue stimuli and so did a third callosotomy patient with sparing of the posterior callosum, including the splenium. Tactile and visual tests showed that the left hemisphere was responsible for language-based responses in the first two patients. The results confirm and extend previous findings in another callosotomy patient, indicating that: (i) taste information from either side of the tongue can reach the left hemisphere in the absence of the corpus callosum; (ii) the ipsilateral input from the tongue to the left hemisphere is more potent functionally than the contralateral input and (iii) in the normal brain, the corpus callosum, specifically its posterior part including the splenium, appears to equalize the effects of the ipsilateral and contralateral gustatory inputs on the left hemisphere. Taken together with evidence about lateralized taste deficits following unilateral cortical lesions, the results also suggest that the gustatory pathways from tongue to cortex are bilaterally-distributed with an ipsilateral predominance that may be subject to individual variations.

Volitional covert orienting to a peripheral cue does not suppress cue-induced inhibition of return.

Detection reaction time (RT) at an extrafoveal location can be increased by noninformative precues presented at that location or ipsilaterally to it. This cue-induced inhibition is called inhibition of return or ipsilateral inhibition. We measured detection RT to simple light targets at extrafoveal locations that could be designated for covert orienting by local or distant cues. We found that cue-induced inhibition cooccurred in an additive fashion with the direct effects of covert orienting, i.e., it detracted from facilitation at attended locations and increased the disadvantage for unattended locations. Thus, cue-induced inhibition cannot be suppressed by a volitional covert orienting to the cued location; the co-occurrence of different facilitatory and inhibitory effects confirms the simultaneous operation of multiple independent attentional mechanisms during covert orienting.

Incomplete gustatory lateralization as shown by analysis of taste discrimination after callosotomy.

The lateral organization of the gustatory pathway in man is incompletely understood. Majority of the studies support an uncrossed projection from each side of the tongue to the cortex, but reports of an opposite crossed organization continue to appear in the neurological literature. We studied the lateral organization of the gustatory pathway in normal controls, a man with a complete callosal agenesis, and a man with a complete section of the corpus callosum, a right anterior-frontal lesion, and language in the left hemisphere. Sapid solutions were applied to one or the other side of the tongue, and subjects reported the taste of the stimulus either verbally or by manually pointing to the name of the taste. There were no differences in accuracy and reaction time between the right and left hemitongues of the controls and the genetically acallosal observer. By contrast, the callosotomy subject showed a constant marked advantage of the left hemitongue over the right for both accuracy and speed of response, though performance with right stimuli was clearly above chance. The left advantage can be attributed to the left hemisphere being favored by the essentially verbal nature of the task, or to the presence of a lesion in cortical gustatory areas in the right hemisphere, or to both factors. Whichever of these hypotheses turns out to be correct, the results unequivocally reject the notion of an exclusively crossed organization of the gustatory pathway from the tongue to the cortex, and favor the notion of a bilaterally distributed organization of this pathway with a marked predominance of the uncrossed over the crossed component.

A possible selective impairment of magnocellular function in compression of the anterior visual pathways.

Two parallel visual systems, the magnocellular (M) and parvocellular (P) pathways, originate from different types of retinal ganglion cells, and are known to be segregated in different portions of the pregeniculate visual pathways. Their relative contribution to two main cortical streams, dorsal and ventral, is still under discussion, but it is reasonable to suppose that selective damage to the M or P subcortical system might interfere with specific aspects of processing within one or the other cortical system. Using two different apparent-motion tasks, we compared the performance of patients affected by compression of the ventral part of the pregeniculate visual pathways with that of normal controls. In the first task, observers detected small displacements of a low-contrast vertical bar, while in the second task they estimated the visible persistence of moving dots. In the first task, patients were impaired with parafoveal displays, especially in the temporal portion of the visual field. In the second task, patients showed reduced suppression of visible persistence at long, but not at short, exposure durations. Three considerations support the hypothesis that these results represent a selective impairment of the M system. First, M axons are more likely to suffer from compression, particularly in the case of a mass growing from below since they are known to occupy a ventral subpial position in the optic chiasm and tract. Second, the performance of patients with a ventral compression is consistent with the characteristics of the response properties of P ganglion cells, which have previously been shown to exhibit elevated and unmodulated thresholds for displacement detection in the macaque monkey. Third, such patients are less sensitive to the inhibitory signals that suppress visible persistence, which probably originate in the M system.

Pathways of interhemispheric transfer in normals and in a split-brain subject. A positron emission tomography study.

We studied with PET the intra- and interhemispheric pathways subserving a simple, speeded-up visuomotor task. Six normal subjects and one patient with a complete section of the corpus callosum (M.E.) underwent regional cerebral blood flow (rCBF) measurements under conditions of lateralized tachistoscopic visual presentations in a simple manual reaction time paradigm. Confirming previous behavioural findings, we found that on average crossed hand and/or hemifield conditions, i.e. those requiring an interhemispheric transfer of information, yielded a longer RT than uncrossed conditions. This difference (0.7 ms) was dramatically larger (45.6 ms) in the callosum-sectioned patient M.E. In normal subjects the cortical areas selectively activated in uncrossed and crossed conditions were different. In the former condition, most activation foci were anterior to the ventral anterior commissure (VAC) plane, whereas in the latter there was a prevalent parietal and occipital activation. This shows that a simple model in which the cortical visuo-motor pathways are similar in the intra- and the interhemispheric condition, with an extra callosal route for the latter, is too simplistic. Furthermore, these results suggest that the bulk of visuomotor interhemispheric transfer takes place through the widespread callosal fibres interconnecting the parietal cortices of the two hemispheres. The pattern of activation in the two crossing conditions was markedly different in M.E., in whom interhemispheric transfer might take place via his intact anterior commissure or subcortical commissures.

Possible recoding of visual space in covert orienting tasks.

Reaction time to lateralized light targets is longer if targets are preceded by light stimuli in the same visual hemifield compared to when they are preceded by light stimuli in the opposite visual hemifield. The effect is probably caused by interactions between implicit oculomotor tendencies and covert shifts of attention. We show here that a similar, but much smaller, ipsilateral RT inhibition can be observed when all stimuli are presented in a display completely lateralized to one hemifield, where ipsilateral and contralateral are defined with respect to the midpoint of the display. The persistence of ipsilateral inhibition with unilateral stimulus displays can be accounted for by a recoding of visual space predicated on the centering of covert attention on the display midpoint rather than on the fixation point. The recoding seems to affect the control of covert attention and perhaps oculomotor control as well.

Paradoxically greater interhemispheric transfer deficits in partial than complete callosal agenesis.

Symptoms of interhemispheric disconnection are typically much less severe in callosal agenesis than after surgical section of the corpus callosum. Sperry [Sperry, R. W., Plasticity of neural maturation. Developmental Biology, 1968, 2 (Suppl.), 306-327.] has attributed this difference to two interconnected factors: (1) the callosal section is usually performed after the brain has lost the maximal degree of functional plasticity associated with the early stages of development and (2) the removal of an already formed structure is more disruptive for functional brain organization than the failure of the same structure to develop. It has been suggested that functional compensation is less efficient if callosal agenesis is partial rather than complete [Dennis, M., Impaired sensory and motor differentiation with corpus callosum agenesis: A lack of callosal inhibition during ontogeny? Neuropsychologia, 1976, 14, 455-469.]. This suggestion is supported by the present findings of partial left-hand anomia, partial left-field alexia and poor tactile cross-localization in a subject with a congenital absence of the posterior part of the corpus callosum due to an arteriovenous malformation. In agreement with many previous studies, similar, though more severe, symptoms of interhemispheric disconnection were found in a subject with a complete section of the corpus callosum, but not in a subject with complete callosal agenesis. Praxic control of the left hand on verbal commands was severely deficient in the callosotomy subject, but it was normal in the subject with callosal hypogenesis. The lesser degree of compensation in partial compared to complete callosal agenesis may be explained by a reduced pressure to develop extracallosal means of interhemispheric communication, contingent on the partial existence of callosal connections, as well as by the later occurrence in development of the causes of callosal hypogenesis compared to those of total callosal agenesis.

Motor representation of the hand in the human cortex: an f-MRI study with a conventional 1.5 T clinical unit.

The purpose of this study was to show a gradient of possible bilateral activation for movements of the non-dominant vs. dominant hand, as well as for areas involved in complex vs. simple hand movements. A standard 1.5 T magnetic resonance imaging (MRI) system has been utilized to localize the cortical motor hand areas, using the blood oxygen level dependent contrast (BOLDc) technique and single-section fast low-angle shot (FLASH) imaging. Ten normal right-handed subjects volunteered for the study. The motor tasks consisted of simple (flexion-extension) finger movements of either hand, and complex movements (finger-to-thumb opposition in a repeating, pre-planned sequence) of the non-dominant hand. Simple movements caused contralateral activation of the primary motor area (MA); ipsilateral activation was observed for the non-dominant hand only. Supplementary motor area (SMA) was also activated, with a clear contralateral prevalence. The ratio of bilateral activation of MA did not change with complex movements of the non-dominant hand, while SMA as well as lateral premotor area were largely bilaterally activated in this task. In conclusion, the ipsilateral MA is activated for movements--even simple--performed with the non-dominant hand. There is widespread functional activity, involving both contralateral and ipsilateral SMA, for complex movements.

Induced astigmatism after near-clear hinge incision.

PURPOSE: To evaluate astigmatism induced by the near-clear hinge incision. SETTING: Casa di Cura Villa Toniolo, Bologna, and Day Hospital Nuova Ricerca, Rimini, Italy. METHODS: The results in 100 eyes having phacoemulsification with a 3.2 or 4.1 mm temporal near-clear hinge incision were evaluated for a maximum of 6 months. Corneal curvature was measured using computerized videokeratography, and surgically induced astigmatism was computed by vector analysis. Surgically induced corneal topographic changes were also evaluated. RESULTS: Mean induced cylinder in the 3.2 mm incision group was 0.4 diopter (D) +/- 0.2 (SD) 6 months after surgery; there was no significant difference in the values at 4 days and 6 months. Mean induced cylinder in the 4.1 mm incision group was similar at 1 and 6 months (0.47 and 0.45 D, respectively). However, it was significantly higher at 4 days (0.56 D). Vector decomposition analysis showed that the with-the-rule component was prevalent and remained constant over 6 months. Topographic analysis showed localized wound-related flattening with minimal central corneal changes. CONCLUSION: The near-clear hinge incision was almost astigmatically neutral and resulted in self-sealing incisions that did not leak.

Rightward attentional bias and left hemisphere dominance in a cue-target light detection task in a callosotomy patient.

Six normal subjects and a callosotomized man with a prefrontal lesion, mostly on the right side, were tested in a reaction time (RT) task involving a key-pressing response to an extrafoveal light target preceded by an extrafoveal light cue. Cues and targets were presented along the horizontal meridian at 4 degrees and 12 degrees on the right and left of fixation. Fixation was maintained throughout each trial. The cue signalled the occurrence of the target within a time window extending from 200 to 4000 misec from the cue, but did not predict target location. Normal controls responded faster to medial than to lateral targets in both fields, but showed no between-field difference, and their RT was not affected by cue location. Furthermore, they showed the so-called 'ipsilateral inhibition' or 'inhibition of return' effect, their RT being longer when cues and targets occurred in the same field than when they occurred in opposite fields. The RT of the callosotomized subject showed a left-right gradient for both cue location and target location, being longest for the leftmost location and shortest for the right locations. In addition, he showed a significant advantage for the right hand regardless of cue and target location, as well as a consistent ipsilateral inhibition in the left field, whereas in the right field there was ipsilateral inhibition only at the two longest stimulus onset asynchronies. These results suggest that, at least under these experimental conditions, there was a rightward orientational bias which reflected the taking over of the control of performance by the left hemisphere. This attentional bias was reminiscent of that seen in patients with hemi-inattention from right hemisphere damage, although the callosotomized patient showed no sign of such hemi-inattention in routine clinical tests. On the basis of several considerations the rightward bias could be attributed to the callosal interhemispheric disconnection rather than to the right prefrontal lesion.