Saccular Projections Research Articles

Intraoperative Rerupture and Surgical Clipping of a Small Superiorly Projecting Anterior Communicating Artery Aneurysm: 2-Dimensional Operative Video.

Anterior communicating artery (ACoA) aneurysms are prone to rupture even at smaller sizes. The surgical management of ACoA aneurysms is highly dependent on the spatial orientation of the saccular projection, categorized as inferior, superior, anterior, or posterior. Superior projecting aneurysms constitute approximately one-third of all aneurysms involving the ACoA. These aneurysms commonly project within the interhemispheric fissure; however, if the aneurysm is not high-riding, it can often be approached via a transsylvian trajectory. The patient presented after subarachnoid hemorrhage with a 3-mm superiorly projecting ACoA aneurysm. The lesion was approached via a right modified orbitozygomatic craniotomy with a transsylvian trajectory. The aneurysm reruptured after minimal manipulation of the dome. Mitigation of the intraoperative rupture was achieved through temporary clip application to bilateral A1 vessels. Bipolar coagulation and placement of 2 permanent clips facilitated final aneurysm occlusion. Postoperative imaging demonstrated patent bilateral A2 flow and no residual aneurysm filling. The patient gave informed consent for surgery and video recording. Institutional review board approval was deemed unnecessary. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Surgical Clipping of an Unruptured Large Inferiorly Projecting Anterior Communicating Artery Aneurysm With Chiasmopathy: 2-Dimensional Operative Video

Anterior communicating artery (ACoA) aneurysms are a frequently encountered cerebrovascular entity that is associated with a high rupture rate at a smaller size and debilitating morbidity and mortality following rupture. The surgical management of ACoA aneurysms is highly dependent on the spatial orientation of the saccular projection, which is categorized as inferior, superior, anterior, or posterior. The inferiorly projecting aneurysms constitute a minority of all aneurysms involving the ACoA. The adherence of the aneurysm dome near the chiasm predisposes these patients to dome avulsion during frontal lobe retraction. This patient presented with a 1-mo history of progressive vision loss and was found to have a large inferiorly projecting ACoA saccular aneurysm measuring 2.04 cm×1.54 cm with resultant chiasmopathy. The lesion was approached via a right modified orbitozygomatic craniotomy, which can provide a more favorable maximal angle of approach to the ACoA complex to avoid brain retraction. Intraoperative adenosine was administered to provide relaxation of the aneurysm dome to augment clip placement. Postoperatively, the patient's chiasmopathy demonstrated near-complete resolution. The patient gave informed consent for surgery and video recording. Institutional review board approval was deemed unnecessary. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Sound-evoked vestibular projections to the splenius capitis in humans: comparison with the sternocleidomastoid muscle.

The short-latency vestibulo-collic reflex in humans is well defined for only the sternocleidomastoid (SCM) neck muscle. However, other neck muscles also receive input from the balance organs and participate in neck stabilization. We therefore investigated the sound-evoked vestibular projection to the splenius capitis (SC) muscles by comparing surface and single motor unit responses in the SC and SCM muscles in 10 normal volunteers. We also recorded surface responses in patients with unilateral vestibular loss but preserved hearing and hearing loss but preserved vestibular function. The single motor unit responses were predominantly inhibitory, and the strongest responses were recorded in the contralateral SC and ipsilateral SCM. In both cases there was a significant decrease or gap in single motor unit activity, in SC at 11.7 ms for 46/66 units and in SCM at 12.7 ms for 51/58 motor units. There were fewer significant responses in the ipsilateral SC and contralateral SCM muscles, and they consisted primarily of weak increases in activity. Surface responses recorded over the contralateral SC were positive-negative during neck rotation, similar to the ipsilateral cervical vestibular evoked myogenic potential in SCM. Responses in SC were present in the patients with hearing loss and absent in the patient with vestibular loss, confirming their vestibular origin. The results describe a pattern of inhibition consistent with the synergistic relationship between these muscles for axial head rotation, with the crossed vestibular projection to the contralateral SC being weaker than the ipsilateral projection to the SCM. NEW & NOTEWORTHY We used acoustic vestibular stimulation to investigate the saccular projections to the splenius capitis (SC) and sternocleidomastoid (SCM) muscles in humans. Single motor unit recordings from within the muscles demonstrated strong inhibitory projections to the contralateral SC and ipsilateral SCM muscles and weak excitatory projections to the opposite muscle pair. This synergistic pattern of activation is consistent with a role for the reflex in axial rotation of the head.

Study of the relationship between cVEMP and ABR 500 Hz

ObjectiveTo evaluate the possible contribution of the saccular projections in generation ABR 500 Hz at high intensity by investigating the relationship between cVEMP and ABR 500 Hz in normal subjects and those with unilateral saccular dysfunction. SubjectsTwenty dizzy adults with unilateral affected cVEMP compared to twenty healthy subjects. MethodsAll subjects were subjected to basic audiological evaluation (pure tone audiometry, speech audiometry and immittancemetry), cVEMP and ABR using 500 Hz tone burst at 90 dB nHL. The dizzy patients within the study group were subjected to VNG to exclude another vestibular affection. The resultsWe found that patient’s abnormal cVEMPs response mostly had prolonged ABR 500 Hz wave V latency, whereas unaffected ears presented with normal findings. ConclusionUsing ABR 500 Hz in the battery approach tests of vestibular assessment can produce valuable data for judgment on the site of a lesion.

The vestibular-auditory interaction for auditory brainstem response to low frequencies.

Since saccular projection is sound sensitive, the objective is to investigate the possibility that the saccular projections may contribute to auditory brainstem response to 500 HZ tone burst (ABR500 HZ). During the case-control research, twenty healthy controls compared to forty selected case groups as having chronic and resistant BPPV were evaluated in the audiology department of Hamadan University of Medical Sciences (Hamadan, Iran). Assessment is comprised of audiologic examinations, cervical vestibular evoked myogenic potentials (cVEMPs), and ABR500 HZ. We found that forty affected ears of BPPV patients with decreased vestibular excitability as detected by abnormal cVEMPs had abnormal results in ABR500 HZ, whereas unaffected ears presented normal findings. Multiple comparisons of mean p13, n23 latencies, and peak-to-peak amplitudes between three groups (affected, unaffected, and healthy ears) were significant. In conclusion, the saccular nerves can be projective to auditory bundles and interact with auditory brainstem response to low frequencies. Combine the cVEMPs and ABR500 HZ in battery approach tests of vestibular assessment and produce valuable data for judgment on the site of lesion. Regarding vestibular cooperation for making of wave V, it is reasonable that the term of ABR500 HZ is not adequate and the new term or vestibular-auditory brainstem response to 500 HZ tone burst is more suitable.

No Effects of Anti-Motion Sickness Drugs on Vestibular Evoked Myogenic Potentials Outcome Parameters

To investigate the effects of meclizine (50 mg), baclofen (10 mg), cinnarizine (20 mg) + dimenhydrinate (40 mg), and promethazine (25 mg) + dextro-amphetamine (5 mg) on the parameters of the vestibular evoked myogenic potential (VEMP) test. Double-blind placebo-controlled prospective randomized trial. University hospital. Twenty-four (first block: baclofen versus placebo) and 20 healthy male subjects (second block: meclizine, cinnarizine + dimenhydrinate and promethazine + dextro-amphetamine versus placebo). VEMP test. Threshold, p13 and n23 latencies, p13-n23 latency difference, p13-n23 peak-to-peak amplitude, mean rectified voltage of the sternocleidomastoid muscle contraction and the corrected amplitude. There were no clinically significant pharmacologic effects on the VEMP outcome parameters. However, there was a statistically significant left-right asymmetry after intake of the combination promethazine + d-amphetamine for the parameters p13 and latency difference. The absence of clinically significant effects can be explained by the predominant presence of the target receptors for the applied drugs in the medial vestibular nucleus, which receives the lowest grade of saccular projections. It also can be hypothesized that the VEMP methodology and techniques in general do not allow determining pharmacologic effects in a healthy group of subjects because of a too small discriminative power. The left-right asymmetry can be explained by a depressive action of the drugs on the central compensation mechanisms. Because there were no significant differences between the VEMP parameters obtained after intake of the placebos of both blocks, we concluded that there were no training effects.

Saccular activations in the brainstem and the cerebellum (fMRI)

The saccular projections in the brainstem and the cerebellum to the uvula and the nodulus have recently been demonstrated in the macaque. The aim of this fMRI study was to determine whether vestibular evoked myogenic potentials (VEMP) which are a routine diagnostic instrument for sacculus function for the past years can activate areas other than the vestibular nuclei in the brainstem and the cerebellum in humans. If so could one also demonstrate a dominant saccular input from either ear in right-handers? Therefore, the differential effects of unilateral VEMP stimulation (500Hz tone burst signal in the right ear while the left ear was plugged for 26s, 13 runs) on subcortical activation were studied in 18 right-handed healthy volunteers (9M, 9 F; mean age 24 years) lying supine in a clinical 1.5 T scanner wearing MRI-suitable piezo-electric headphones (Jaencke, Zuerich). Each volunteer underwent three randomised sessions: 1. One with a 95 dB 500Hz tone burst signal for which VEMPs had been recorded from the sternocleido-mastoideus muscle outside the scanner before. 2. One control session with a similar sub threshold 65 dB 500Hz tone burst signal which could not trigger VEMPs. 3. The third control trial consisted of a 95 dB white noise signal to differentiate the expected bold responses from the pure loudness of the auditory stimulation. Random effects statistical analysis was done with SPM2 (p<0.005, uncorrected) after motion correction, coregistration to a new specific template for the brainstem and the cerebellum, masking, normalization and smoothing. Unilateral saccular stimulation from the right ear gave activations only in the right dentate nucleus and the nodulus. These could not be seen after stimulation of the left ear. But the VEMP stimulation from either side resulted in a significant deactivation of the declive and culmen bilaterally. In a paired t-test right side vs. left side, which excluded the auditory effects (95 dB click tone bursts vs. 65 dB click tone bursts) significant activations were found in the right dentate nucleus, the nodulus, the right inferior semilunar lobule and the inferior vermis. This is the first demonstration of vestibular otolith activations in humans in the brainstem and cerebellum by means of fMRI. We found a dominance for the saccular input from the right ear. Monaural otolith stimulation from the right side in right-handers caused significant activation in the nodulus and right dentate nucleus and simultaneous deactivations of the culmen and declive.

Multiple Mechanosensory Modalities Influence Development of Auditory Function

Sensory development can be dependent on input from multiple modalities. During metamorphic development, ranid frogs exhibit rapid reorganization of pathways mediating auditory, vestibular, and lateral line modalities as the animal transforms from an aquatic to an amphibious form. Here we show that neural sensitivity to the underwater particle motion component of sound follows a different developmental trajectory than that of the pressure component. Throughout larval stages, cells in the medial vestibular nucleus show best frequencies to particle motion in the range from 15 to 65 Hz, with displacement thresholds of <10 mum. During metamorphic climax, best frequencies significantly increase, and sensitivity to lower-frequency (<25 Hz) stimuli tends to decline. These findings suggest that continued sensitivity to particle motion may compensate for the considerable loss of sensitivity to pressure waves observed during the developmental deaf period. Transport of a lipophilic dye from peripheral end organs to the dorsal medulla shows that fibers from the saccule in the inner ear and from the anterior lateral line both terminate in the medial vestibular nucleus. Saccular projections remain stable across larval development, whereas lateral line projections degenerate during metamorphic climax. Sensitivity to particle motion may be based on multimodal input early in development and on saccular input alone during the transition to amphibious life.

Saccular Projections in the Human Cerebral Cortex

The cerebral cortical areas processing saccular information were investigated in human subjects using the fMRI method and loud clicks, which selectively activate the saccule. The results were compared with previous vestibular evoked potential (VEP) studies in anesthetized patients following vestibular nerve stimulation. Nine normal subjects participated in fMRI studies. By comparing the cortical areas activated by a click at 85 dB (auditory activation) with those activated by 102 dB (auditory plus saccular activation), the following cortical areas were selectively activated by saccular stimulation: intraparietal sulcus, frontal eye fields, prefrontal cortex, and postcentral gyrus, in addition to insula, supplementary motor area, and anterior and posterior cingulate cortex. Previous VEP studies also revealed similar activation areas by vestibular nerve stimulation with latencies at 6 ms, suggesting that the shortest pathways for activation of cerebral cortical neurons from the labyrinth are trisynaptic, with a relay in the thalamus. The activated areas are also consistent with results in previous studies using caloric stimulation, which primarily activates horizontal semicircular canals. These results suggest that canal and otolith information is processed largely by similar cortical areas in humans. Multiple cortical areas activated by these studies suggest that these areas are involved in different aspects of processing vestibular information. The saccular projections to the prefrontal and frontal cortex suggest that these areas are involved in planning motor synergies to counteract loss of equilibrium.

Infection of an internal carotid artery plaque with vancomycin resistant enterococcus

Eur J Vasc Endovasc Surg 26, 332-333 (2003)

The neuronal system of the saccus vasculosus of trout (Salmo trutta fario and Oncorhynchus mykiss): an immunocytochemical and nerve tracing study.

The neuronal system of the saccus vasculosus of two species of trout was studied with immunocytochemical methods and carboindocyanine-dye (DiI) tract-tracing. The cerebrospinal-fluid-contacting neurons of the saccus were immunoreactive for gamma-aminobutyric acid (GABA), glutamic acid decarboxylase (GAD), and neuropeptide Y (NPY). Immunostaining of alternate sections of the saccus vasculosus of fry with anti-GAD and anti-NPY indicated that these substances were colocalized. The tractus sacci vasculosi and the neuropil of the nucleus sacci vasculosi were also immunoreactive to these substances. The GABA, GAD, and neuropeptide Y immunoreactivity of the saccus vasculosus system appeared early in trout ontogeny. After applying DiI to various levels of the tractus sacci vasculosi of adult trout, we observed massive bilateral saccular projections to the nucleus sacci vasculosi and could follow the course of the sacco-thalamic tract. This tract extended in the subependymal region of the thalamus rostral to the nucleus sacci vasculosi and split into two small tracts that reached the subhabenular-preoptic region. Sacco-thalamic fibers formed extensive periependymal plexuses along their trajectory. Interestingly, no clear evidence of the existence of a saccopetal system was obtained. On the basis of these results, we postulate that the saccus vasculosus system modulates the function of centers of the posterior tubercle and periventricular thalamus.

Central Projections from Singular Parts of the Vestibular Labyrinth in the Guinea Pig

Primary afferent projections from singular parts of the vestibular labyrinth were studied in the guinea pig. The posterior ampullary nerve, the common trunk of the anterior and lateral ampullary nerves, as well as fibers innervating the macula sacculi or the macula utriculi were traced with crystals of horseradish peroxidase (HRP) lyophilisate. Posterior, as well as anterior and lateral ampullary fibers were found to project extensively to the superior vestibular nucleus, but also reached the other main vestibular nuclei. Saccular fibers projected mainly to the lateral parts of the lateral vestibular nucleus and to the adjoining descending and superior vestibular nuclei as well as to group y. Modest projections could be followed to the medial vestibular nucleus. Furthermore, a distinct saccular projection to the cochlear nuclei was evident. Utricular projections reached the four main vestibular nuclei with a denser accumulation of fibers within ventral parts of the lateral, descending and superior vestibular nuclei.

Differentiation of Aneurism from Infundibulum of the Posterior Communicating Artery

A ARTERIOGRAPHIC demonstration of aneurisms encountered in the lower portion of the C1 segment of the internal carotid artery, below the origin of the anterior choroidal artery and at, or near, the junction with the posterior communicating artery, has remained a vexatious problem because of the danger of interpreting a benign projection of contrast material as representing an aneurismal dilatation. The subject has received little attention although discussions with colleagues reveal an acute awareness of the problem gained, in part, at the expense of negative surgical explorations. The radiographic anatomy of this site has been discussed by Saltzman ~ in noting that the posterior communicating aI'tery is often dilated and funnel-shaped at its point of origin at the carotid siphon, an area which may be termed the infundibulum. Although the infundibulum can fill with contrast material from the carotid artery, the subsequent course of a posterior communicating artery with a small lumen may not be visualized because of failure to fill or because of the low density of contrast material in the small-caliber vessel. The resultant saccular projection of contrast material arising from the supraclinoid internal carotid artery may be readily confused with an aneurism. Five cases are presented in which the apparent aneurism was actually the infundibulum of the posterior communicating artery. The problems encountered in differentiating between the two alternatives are noted and suggestions are offered for establishing the correct diagnosis.