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A 57-year-old patient presented with a long history of minimally symptomatic mitral valve prolapse (MVP). The patient eventually developed severe mitral regurgitation (MR) and clinical evidence of congestive heart failure over 10 years duration before admission. He described a 34-year history of MVP. A transesophageal echocardiography examination demonstrated left atrial enlargement and severe prolapse of the posterior mitral leaflet associated with severe MR to the dome of the left atrium. Left ventricular size and function were normal. A quadrangular resection of prolapse segment and placement of a posterior annuloplasty ring were used to successfully repair the valve using a minimally invasive approach. The current case emphasizes that patients with MVP complicated by MR may remain clinically asymptomatic for prolonged periods, only to subsequently develop left atrial enlargement, severe MR, and congestive heart failure late in the natural history of the disease.

1. Extracellular single-cell recordings were made from the cerebellar thalamus, the ventro-posterior lateralis par caudalis (VPLc) and motor cortex of three conscious monkeys. Recordings were made from the thalamus as well as the cortex in two monkeys. In all, recordings were made from the thalamus in four hemispheres and from the motor cortex in four hemispheres. The animals were trained to permit a detailed examination when relaxed. Unexpected perturbations were applied to the wrist. Seventy-seven wrist-related neurones were recorded in the cerebellar thalamus, forty-two neurones from the VPLc and eighty-four neurones in motor cortex. 2. Cerebellar nuclear stimulation was used to physiologically identify thalamic neurones receiving input from the cerebellum. The location of all neurones was verified histologically. 3. The majority of cerebellar thalamic neurones had deep sensory receptive fields related to a single muscle, a group of synergists or a single joint. There was a distinct topographical organization. These fields were similar to sensory fields in motor cortical neurones, but had higher thresholds. 4. VPLc neurones had discrete deep or cutaneous sensory fields, or a combination of these fields, which suggests convergence. VPLc neurones had fields with lower thresholds than cerebellar thalamic neurones. The somatotopically located forelimb area in the VPLc was posterior to and continuous with the forelimb area in the cerebellar thalamus. 5. VPLc neurones responded with a shorter latency to wrist perturbations than did cerebellar thalamic neurones. VPLc neurones with deep sensory fields changed firing significantly earlier than those with cutaneous fields. The VPLc is likely to be the major source of sensory input to the motor cortex, and based on the results of this study we suggest that the VPLc is the thalamic nucleus best placed to transmit short-latency afferent input from the forelimb. 6. The timing of the neuronal discharge of cerebellar thalamic and VPLc cells, which resulted from perturbations of the wrist, was best linked to the duration of movement rather than its amplitude. The cells began firing as soon as the velocity changed sign and continued firing until the sign of the velocity changed again. In subsequent corrective movements neuronal discharge in the VPLc appeared to also encode movement acceleration.

1. Three monkeys were trained to perform a reaction-time task of the wrist and single-cell recordings were made from the motor cortex (eighty-four cells), ventro-posterior lateralis par caudalis (VPLc) (forty-two cells) and cerebellar thalamus (seventy-seven cells). 2. The majority (43/77, 56%) of cerebellar thalamic neurones fired phasically during movement, whereas in the motor cortex most neurones (53/84, 64%) had a phasic-tonic discharge pattern. Most neurones in both locations discharged in relation to the direction of movement (reciprocal pattern). 3. The cerebellar thalamus is unlike the motor cortex in that it does not usually encode a signal for force or joint position in its discharge. 4. Twenty-two per cent (17/77) of cerebellar thalamic neurones had a period of reduced discharge rate before the phasic burst of activity, and represent a pattern of discharge not seen in motor cortex or VPLc neurones. 5. The onset of phasic activity in the cerebellar thalamus was significantly later (average 94 ms) than in the motor cortex but occurred just before electromyogram (EMG) activity. The phasic activity in the cerebellar thalamus usually ended before the phasic component of motor cortex discharge was completed. 6. Phasic activity in VPLc neurones commenced after the onset of EMG discharge and on average 26 ms after the commencement of movement. Most neurones with deep sensory receptive fields fired with a reciprocal pattern, while neurones with cutaneous fields usually fixed bidirectionally in relation to the task. Almost one-third of neurones signalled force and a similar number had discharge levels that encoded characteristics of the joint position. 7. The duration of discharge of VPLc neurones during the voluntary movement was marginally less than the duration of the movement velocity peak and the VPLc may therefore be signalling the duration of the velocity. Phasic activity in cerebellar thalamic neurones fired for a duration similar to the VPLc neurones, but commenced before the movement. Therefore, if the cerebellar thalamus is carrying information about the duration of the velocity, it does so before the movement starts. 8. The phasic burst of activity in cells of the cerebellar thalamus is timed so that it can contribute to the later component of the phasic burst of motor cortical discharge. Thus we speculate that in skilled, ballistic movements, the cerebellum may provide a response which travels via the cerebellar thalamus and helps to determine the magnitude and duration of the phasic part of cortical discharge.(ABSTRACT TRUNCATED AT 400 WORDS)

1. Extracellular recordings were made in three monkeys while recording from neurones in the motor cortex (eighty-four cells), ventro-posterior lateralis pars caudalis (VPLc, forty-two cells) and cerebellar thalamus (seventy-seven cells). 2. This experiment was designed to produce active and reflex movements of varying velocities in order to study the relationship between amplitude of velocity and magnitude of neuronal discharge of thalamic neurones. The active movements were voluntary rapid alternating movements (RAMs) of the wrist and the reflex movements were produced by forcibly oscillating the wrist joint between frequencies of 1 and 7 Hz (forced oscillations). 3. This study was also designed to examine cerebellar influences on a reflex path, namely the transcortical reflex loop. Forced oscillations were predicted to provide circumstances where active damping was required to prevent excessive oscillations in the reflex path. Rapid alternating movements of the wrist were predicted to provide circumstances where oscillations at the natural frequency in that reflex path would support and propagate the movements. 4. Forced oscillations from 1 to 7 Hz produced movements of different velocities. VPLc and cerebellar thalamic neurones discharged in relation to the duration of movement in a particular direction, but their discharge levels were unrelated to the magnitude of the velocity. Motor cortex neurones fired in a pattern which was related to the timing but not the magnitude of the acceleration. 5. In forced oscillations of the wrist the resonant frequency was between 3 and 7 Hz. They may be controlled in part by a transcortical reflex. The cerebellar thalamic neurones did not fire before motor cortex neurones. Therefore, it is unlikely that the cerebello-thalamo-cortical pathway is necessary to damp these potentially unstable oscillations by an effect on antagonist-related cortical neurones. 6. Rapid alternating movements (RAMs) of monkeys' wrists were performed in a stereotyped fashion over a narrow range of frequencies with the greatest displacement in joint angle and peak velocity at the natural frequency of 3-5 Hz. 7. During the performance of RAMs, neuronal discharge modulated sinusoidally in the VPLc, cerebellar thalamus and motor cortex. There was no relationship between velocity and neuronal discharge of the cerebellar thalamic and motor cortical neurones but there did appear to be a relationship between velocity and VPLc neuronal discharge. 8. The onset of electromyogram (EMG) discharge changed earlier than neuronal discharge in the motor cortex and thalamus during the performance of RAMs.(ABSTRACT TRUNCATED AT 400 WORDS)