Severe sinus bradycardia in a patient with Rett syndrome: a new cause for a pause?

Rett syndrome is a progressive disorder seen primarily in young females. It is characterized by autonomic dysfunction affecting many organ systems. Although sudden death is common in these patients, little is known about the cardiovascular manifestations of this dysautonomia. Earlier reports focused on the role of sympathetic overactivity manifest as reduced heart rate variability and prolonged QT intervals indicating a propensity for lethal ventricular arrhythmias. Bradyarrhthmias and sinus node dysfunction, however, have not previously been reported. We describe a 2-year-old with Rett syndrome and severe sinus bradycardia requiring a pacemaker implant. This case represents the first description of a new cardiovascular manifestation of Rett syndrome and may provide an explanation for sudden and unexpected death in some of these patients.

Electrophysiological examination of the representation of the face in the suprasylvian gyrus of the ferret: a correlative study with cytoarchitecture

Using high-resolution microelectrode mapping methods, we explored the organization of the face representation within the primary somatosensory cortex of ferrets, finding evidence for at least two and probably four representations of the face distributed consecutively from anterior to posterior along the long axis of the suprasylvian gyrus. Examination of the cytoarchitecture (Rice et al., this issue) revealed that these four areas corresponded to four different cytoarchitectonic fields within the crown of the suprasylvian gyrus. The two central, most completely defined representations were oriented so that the dorsal cutaneous surfaces of the face were represented on the lateral side of the gyrus, while the perioral and ventral surfaces were represented on the medial side. The rostral-to-caudal organization within these two representations was reversed; the glabrous rhinaria were represented at the opposite ends of the maps, and penetrations progressively further away from the cortex serving the rhinaria encountered neurons activated by sites progressively more caudal on the face. Receptive fields obtained more rostrally on the gyrus suggested another reversal, implying a third representation. A small area with large receptive fields near the caudal and medial border of the two central maps suggested the presence of a fourth representation. Since the projections of adjacent skin surfaces overlapped considerably, cortical sites serving a particular cutaneous surface were illustrated as enclosed areas that overlapped the territories of other, adjacent representations. The results of this study and of others suggest a need for a re-evaluation of the hypothesis establishing a homology between the representation found in area 3b of primates and that of the primary somatosensory area in nonprimates.

Cytoarchitecture of the ferret suprasylvian gyrus correlated with areas containing multiunit responses elicited by stimulation of the face

The cytoarchitecture was studied in a segment of the ferret suprasylvian gyrus containing at least two and possibly four somesthetic representations of the face that were observed in the primary somatosensory cortex. These representations were restricted to the crown of the gyrus and were surrounded by somesthetically unresponsive cortex that extended down both sides to the base of adjacent sulci. Numerous cytoarchitectonic subdivisions were found on a qualitative basis, and were confirmed quantitatively by cluster analyses and relevant statistical tests of 10 prominent features from layers III, IV, and V. Four distinct cytoarchitectonic subdivisions, each with a well-developed and homogeneous granular layer IV, were found distributed from anterior to posterior along the crown of the gyrus at sites corresponding to the locations of the four facial representations. The surrounding unresponsive cortex had a fragmented cytoarchitecture, especially along the medial bank and base of the coronal sulcus. This unresponsive cortex separated the facial representations from the body representations, which were located on the adjacent posterior cruciate gyrus. Most of the unresponsive subdivisions had a heterogeneous or agranular layer IV and fairly well-developed sublamination in layer III, which may be indicative of extensive corticocortical connections. One set of unresponsive subdivisions had comparable cytoarchitectures that directly bordered the facial representations. Another set of unresponsive subdivisions with comparable architectures occupied most of the lateral bank of the gyrus. The implications of multiple representations and cytoarchitectonic fragmentation of the ferret primary somatosensory cortex are discussed in relation to the organization of the primary somatosensory cortex in other species.