Intra-operative deep brain stimulation of the periaqueductal grey matter modulates blood pressure and heart rate variability in humans.

INTRODUCTION: Deep brain stimulation applied to the periaqueductal grey matter (PAG) of the midbrain in humans has been shown to increase or decrease arterial blood pressure during rest and to resist the postural fall on standing. The mechanism by which this effect is elicited is unknown. We hypothesize that PAG stimulation modulates performance of the autonomic nervous system. METHODS: Five consecutive male patients of a mean age of 49.1 years underwent PAG stimulation for intractable pain syndromes. Intra-operatively, blood pressure and heart rate were recorded continuously while patients were awake (four patients) or under general anesthesia (one patient). Recordings were made for 100 sec before stimulation, 100 sec during stimulation at one or two electrode locations within the PAG, and for 100 sec after stimulation. RESULTS: Stimulation altered not only systolic and diastolic blood pressure but also heart rate. During stimulation, systolic blood pressure increased in three electrode positions by 7.2-10.2 mmHg, decreased in two electrode positions by 3.1-11.5 mmHg, and was unchanged in two electrode positions. Heart rate variability also changed during stimulation. Percentage systolic blood pressure change was positively correlated with change in high-frequency power (Pearson's r= 0.685, p= 0.09, N= 7), low-frequency : high-frequency power ratio (r= 0.667, p= 0.10, N= 7), and low-frequency power (r= 0.818, p= 0.02, N= 7), the latter of which was statistically significant. The percentages of the variance explained (r(2)) were 46.9, 44.5, and 66.9, respectively. CONCLUSIONS: PAG stimulation modulates autonomic nervous system activity and thereby elicits changes in cardiovascular performance. Understanding of the mechanisms by which this therapy causes cardiovascular modulation will inform future innovation in this field with the aim of improving the efficacy and safety of patient treatment options.

Disseminated intravascular coagulation after isolated mild head injury.

A rare case is described of acute disseminated intravascular coagulation (DIC) following isolated mild head injury with acute subdural haematoma, coagulopathy onset preceding craniotomy. Surgical treatment of the cause followed by swift diagnosis and treatment soon after surgery enabled a good outcome. Post-operative recollection of subdural and extadural blood was treated by further surgery. DIC following isolated mild head injury without axonal damage is rare, but fatal if missed. Thrombocytopaenia in head injured patients should be investigated expediently. Post-operative interim imaging (if not standard practice) should also be considered to exclude haemorrhagic recollection requiring further surgery.

Deep brain stimulation for movement disorders and pain.

Deep brain stimulation (DBS) is an expanding field within neurosurgery. With many neurosurgeons performing relatively small numbers of these procedures, detailed descriptions of the technical aspects and nuances of DBS may be worthwhile. We describe our technique for DBS, based on over 300 procedures. This methodology continues to evolve and is refined according to our own experience, our observations of others, technological innovations, and information derived from the neurosurgical literature. The indications for DBS in our service are outlined, the anatomical targets described, and the anaesthetic and surgical aspects detailed.

Elevated gamma band power in humans receiving naloxone suggests dorsal periaqueductal and periventricular gray deep brain stimulation produced analgesia is opioid mediated.

BACKGROUND: The midbrain periaqueductal and periventricular gray (PAVG) region is important for pain and autonomic modulation. We have previously described changes in blood pressure dependent upon dorsal or ventral electrode positioning with PAVG deep brain stimulation (DBS), yet controversy exists about whether DBS acts via endogenous opioid release. METHOD AND RESULTS: We combined local field potential (LFP) recording from PAVG DBS electrodes in humans with naloxone and saline infusions to determine whether dorsal and ventral PAVG DBS act through opioidergic or other mechanisms. Four awake human subjects were investigated. DBS were implanted contralateral to the painful body part. Electrode contact positions were mapped using MRI and brain atlas information. Naloxone then saline were randomly administered to the blinded subjects and pain rated using a numeric pain rating scale at 30s intervals for 3 min. Two subjects received dorsal DBS electrodes and two had ventral placements. Significantly elevated gamma frequency band (30-90 Hz) power concomitant with pain exacerbation was found with naloxone versus both saline and rest in dorsal not ventral PAVG LFPs (p<0.005). Significantly elevated delta frequency band (0-4 Hz) power (p=0.001) was seen in one ventral PAVG subject with both naloxone and saline infusions. CONCLUSIONS: Dorsal PAVG DBS may reduce pain by augmenting endogenous opioid release. Elevated gamma oscillations enhance awareness of worsening pain with opioid blockade. Ventral PAVG DBS may act by separate possibly autonomic mechanisms. Increased delta oscillations indicate a survival rhythm involved in the initiation of passive coping responses to homeostatic changes.