Path integration deficits during linear locomotion after human medial temporal lobectomy

Animal navigation studies have implicated structures in and around the hippocampal formation as crucial in performing path integration (a method of determining one\u27s position by monitoring internally generated self-motion signals). Less is known about the role of these structures for human path integration. We tested path integration in patients who had undergone left or right medial temporal lobectomy as therapy for epilepsy. This procedure removed approximately 50% of the anterior portion of the hippocampus, as well as the amygdala and lateral temporal lobe. Participants attempted to walk without vision to a previously viewed target 2-6 m distant. Patients with right, but not left, hemisphere lesions exhibited both a decrease in the consistency of path integration and a systematic underregistration of linear displacement (and/or velocity) during walking. Moreover, the deficits were observable even when there were virtually no angular acceleration vestibular signals. The results suggest that structures in the medial temporal lobe participate in human path integration when individuals walk along linear paths and that this is so to a greater extent in right hemisphere structures than left. This information is relevant for future research investigating the neural substrates of navigation, not only in humans (e.g., functional neuroimaging and neuropsychological studies), but also in rodents and other animals

Medial temporal lobe roles in human path integration

Path integration is a process in which observers derive their location by integrating self-motion signals along their locomotion trajectory. Although the medial temporal lobe (MTL) is thought to take part in path integration, the scope of its role for path integration remains unclear. To address this issue, we administered a variety of tasks involving path integration and other related processes to a group of neurosurgical patients whose MTL was unilaterally resected as therapy for epilepsy. These patients were unimpaired relative to neurologically intact controls in many tasks that required integration of various kinds of sensory self-motion information. However, the same patients (especially those who had lesions in the right hemisphere) walked farther than the controls when attempting to walk without vision to a previewed target. Importantly, this task was unique in our test battery in that it allowed participants to form a mental representation of the target location and anticipate their upcoming walking trajectory before they began moving. Thus, these results put forth a new idea that the role of MTL structures for human path integration may stem from their participation in predicting the consequences of one's locomotor actions. The strengths of this new theoretical viewpoint are discussed

Anterior cervical fusion versus minimally invasive posterior keyhole decompression for cervical radiculopathy

Background: Treatment modalities for degenerative cervical spine disease are widely debated and refined as new surgical techniques are developed. The current case series compares two common cervical spine procedures, anterior cervical discectomy and fusion (ACDF) and minimally invasive posterior keyhole foraminotomy (MIPKF). The decision making process of the two surgical approaches is discussed, and the long term outcomes are presented. Methods: A retrospective chart review of surgical patients having either an ACDF or MIPKF with an extensive chart review. Over 570 patient charts were identified and reviewed between 1994 and 2011. After exclusion, a total of 268 patients were identified in the ACDF group, and 112 patients were identified in the MIPKF group. Primary outcome measurement was the need for any reoperation, whether at the same level or adjacent levels due to recurrence of disease or adjacent level disease. Results: An average follow-up of 11.8 (±3.0) years in the ACDF group and 6.4 (±4.4) years in the MIPKF group was determined over a 17 year period. There was a reoperation rate of 2.6% in the ACDF group and 2.7% in the MIPKF group during the 17 year time period. Conclusion: ACDF has been demonstrated to be an effective surgical procedure in treating degenerative spine disease in patients with radiculopathy and/or myelopathy. However, in a population with isolated radiculopathy and radiological imaging confirming an anterolateral disc or osteophyte complex, the MIPKF can provide similar results without the associated risks that accompany an anterior cervical spine fusion

0209

Thoracic disc herniation has always carried with it the potential for serious adverse neurological consequences if not treated appropriately. The authors review the historical evolution of treatment for thoracic disc herniation from the early surgical series using dorsal approaches (which were known to involve a significant risk of paraplegia) to later surgical series in which lateral and then ventral approaches to the disc were increasingly emphasized, with significant improvement in patient outcome. The evolution of minimally invasive thoracoscopic techniques is discussed, together with the results of several surgical series demonstrating significant reductions in morbidity compared with more traditional methods. The technique of thoracoscopic discectomy is presented in detail. KEY WORDS • thoracic spine • herniated disc • thoracoscopic surgery • endoscopy • minimally invasive surgery Neurosurg. Focus / Volume 9 / October, 2000 1 Abbreviations used in this paper: CT = computerized tomography; LECA = lateral extracavitary approach; LPEA = lateral parascapular extrapleural approach; MR = magnetic resonance; VATS = video-assisted thoracoscopic surgery; 3D = three-dimensional