Orthostatic hypotension is differentially associated with the cerebellar versus the parkinsonian variant of multiple system atrophy: a comparative study.

Orthostatic hypotension (OH) is a cardinal feature of autonomic failure in multiple system atrophy (MSA); however, there are few comparative data on OH in the motor subtypes of MSA. In the present retrospective study, postural blood pressure drop after 3 min of standing was determined in 16 patients with the cerebellar variant of MSA (MSA-C) and in 17 patients with the Parkinson variant (MSA-P). Twenty idiopathic Parkinson's disease (IPD) patients matched for age, sex, disease duration and dopaminergic therapy served as control group. OH frequency and severity were more pronounced in MSA-C followed by MSA-P and IPD. Differences in brainstem pathology are likely to account for the tight association of MSA-C and OH. A simple standing test should be obligatory in the work-up of patients with sporadic late-onset ataxias.

Changes in cerebral oxygenation and haemodynamics during postural blood pressure changes in patients with autonomic failure.

Patients with autonomic failure suffer severe postural hypotension that may be associated with symptoms of cerebral hypoperfusion. This study utilized near-infrared spectroscopy (NIRS) to measure changes in cerebral oxygenation and haemodynamics during the head-up tilt table test in 18 patients with autonomic failure and 10 healthy age-matched volunteers. Heart rate, blood pressure (MAP), oxygen saturation, cerebral tissue oxygen index (TOI) and total cerebral haemoglobin concentration [HbT] were measured continuously. In patients with autonomic failure there was a mean (SD) reduction in MAP of 46.7 (26.5) mmHg (p < 0.005) associated with a reduction in TOI of 8.6 (6.2)% (p < 0.005) during the head-up tilt table test. In healthy volunteers mean (SD) MAP rose by 12.3 (8.0) mmHg (p < 0.005) and TOI fell by 2.6 (3.2)% (p < 0.05). There was a mean (SD) reduction in [HbT] of 3.09 (2.82) micromol l(-1) (p < 0.005) in patients, equivalent to a decrease in cerebral blood volume of 0.2 (0.18) ml/100 g. There were no changes in [HbT] in the healthy volunteers. Postural hypotension in patients with autonomic failure is associated with a substantial decrease in absolute cerebral oxygenation measured by NIRS and this might reflect a critical reduction in cerebral oxygen delivery.

Differences in overshoot of blood pressure after head-up tilt in two groups with chronic autonomic failure: pure autonomic failure and multiple system atrophy.

On head down tilt to the supine horizontal position (tilt reversal) after head up tilt (HUT), patients with orthostatic hypotension may show an increase in blood pressure (BP) relative to baseline readings. We assessed this BP overshoot in 8 patients with pure autonomic failure (PAF, 64+/-13 years) and 8 patients with multiple system atrophy (MSA, 66+/-10 years). BP was intermittently measured during pre-tilt supine, HUT (60 degrees , 10 min), and post-tilt supine periods. In addition, beat-to-beat BP was measured continuously using the Portapres model 2 device to calculate stroke volume (SV), cardiac output (CO) and total peripheral resistance (TPR). There was systolic BP overshoot of > or = 15 mmHg after tilt reversal in 5 out of 8 PAF, but in only one of 8 MSA. A mean increase of systolic BP in PAF was significantly higher than that in MSA (p<0.01). TPR increased over baseline level after tilt reversal, although there was no significant difference. SV and CO levels during the post-tilt supine period were similar to baseline levels. In conclusion, BP overshoot was prominent in the PAF group but not in the MSA group. The phenomenon of BP overshoot while supine, especially in PAF, may have implications for long term cardiac and vascular damage in such patients.

Rate of change in cerebral oxygenation and blood pressure in response to passive changes in posture: a comparison between pure autonomic failure patients and controls.

The cardiovascular and cerebrovascular responses to head-up postural change are compromised in pure autonomic failure (PAF) patients because of sympathetic denervation. The aim of this study was to characterize the rate of change of systemic mean blood pressure (MBP) and cerebral haemodynamics in response to passive posture changes. Nine PAF patients and 9 age-matched controls took part in this study. MBP and oxy- (O2Hb), deoxy-haemoglobin (HHb), and tissue oxygenation index (TOI) on the forehead were continuously monitored non-invasively using the Portapres and near-infrared spectroscopy (NIRS), respectively. From visual inspection of the haemoglobin difference signal (Hb(diff) = O2Hb-HHb), seven distinct phases were marked (1: supine, 2: start passive tilt, 3: head up to 60 degrees degrees, 4: end of tilt, 5: tilt reversal, 6: return to supine, 7: rest); the same time points were used for all of the other signals. For each phase, the slope was calculated using a linear regression algorithm. Significant differences were found between PAF patients and controls in the Hb(diff) slope magnitudes for phases 3 (P < .05) and 5 (P = .01), and the duration of phase 2 (P < .05). MBP slope magnitudes showed significant differences for phases 2 (P < .01) and 5 (P < .01). These differences in the rate of change suggest differences in blood vessel resistance related to sympathetic activation.

Postural variation in intraocular pressure in primary chronic autonomic failure.

Patients with syndromes of generalised autonomic failure often have extreme posture-related lability of blood pressure, with both orthostatic hypotension and recumbent hypertension. Whether these changes influence intraocular pressure (IOP) is not known. Mean arterial pressure (MAP) and IOP were measured in response to variations in posture between +45 degrees and -20 degrees in 8 normal subjects and 9 subjects with primary generalised chronic autonomic failure (AF). With postural change normal subjects showed minimal change in MAP (p=0.6) and small but significant changes in IOP (p < 0.001). Subjects with AF showed large and significant changes in both MAP (p < 0.001) and IOP (p < 0.001). Two AF subjects had raised IOP when recumbent, despite normal IOP at +45 degrees. There was significant covariance of MAP and IOP (p < 0.001 overall, p=0.004 in normal subjects, p=0.006 in AF subjects). However, individually, those patients with large changes in IOP could not be predicted from changes in MAP. These data show that patients with autonomic failure are subject to large posture-related changes in IOP. These appear to be related to the large posture-induced changes in systemic blood pressure which occur in these patients.