Richard J. Moulton

Monitoring severe head injury : a comparison of EEG and somatosensory evoked potentials

We report on our experience with long-term monitoring of the EEG power spectrum and somatosensory evoked potentials (SSEPs) in 103 patients with severe closed head injury (Glasgow Coma Scale-GCS < or = 8). Patients were monitored for an average of 5 days post injury and monitoring was terminated when they died, regained consciousness or their intracranial physiologic parameters (primarily intracranial pressure-ICP) were stable for 2-3 days. Patients were treated according to a standard protocol that included mechanical ventilation, sedation, and neuromuscular blockade. At 7 of 9 twelve hour time intervals post injury, SSEPs were significantly (p < .05) different between outcome groups using the Glasgow Outcome Score collapsed to 3 categories. The percent slow (delta) activity in the EEG was not significantly different between outcome groups at any time point, post injury. The total power in the EEG power spectrum differed only at the last time epoch post injury (108 hr.). Based on the superior prognostic capabilities of the SSEP, we routinely base critical management decisions on SSEP values. We have not been able to rely on EEG parameters for these same decisions due to the lack of clear distinction between good and poor prognosis groups based on common EEG parameters.

Isolated suprascapular nerve palsy : a review of nine cases

BACKGROUND In nine patients, suprascapular nerve palsy followed serious accidents associated with fractures of the cervical vertebrae, clavicle or scapula and after weight lifting, wrestling and a fall on the elbow or shoulder. METHOD All patients were examined as to muscle wasting, weakness and shoulder fixation. EMG examination was done in all cases and six patients underwent surgical exploration. RESULTS The palsy was incomplete on clinical and EMG examination in all patients. On exploration, scarring, entrapment, tethering or kinking at the suprascapular notch was four and two had post-traumatic neuromas. CONCLUSIONS In contrast to published studies, none of our patients presented with shoulder pain, a spontaneous onset nor with involvement limited to the infraspinatus muscle. The differential diagnosis should include C5 root lesion, brachial plexus neuritis, frozen shoulder and tear of the rotator cuff.

Somatosensory evoked potentials and intracranial pressure in severe head injury

The purpose of this study was to explore the relationship between neurologic function, using a quantitative measurement of continuous somatosensory evoked potentials (SSEPs), and intracranial pressure (ICP) following traumatic brain injury. During a 6 year period, severely head-injured patients with a Glascow Coma Scale < or = 8 who were not moribund were monitored with SSEPs and ICP measurements. SSEPs from each hemisphere and ICP were recorded hourly for each patient. Neurologic outcomes were scored using the Glasgow Outcome Scale at three months post injury. Although initial SSEP amplitude did not correlate well with outcome, final SSEP summed peak to peak amplitude from both hemispheres (p = .0001), the best hemisphere (p = .0004), and the worst hemisphere (p = .0001) correlated well with the Glasgow Outcome Scale groups. Of a total of 72 patients, 40 had deteriorating SSEPs and 32 had stable or improving SSEPs. Peak ICP values were not statistically different in these groups (p = .6). Among patients with deteriorating SSEPs, 52.5% lost the greatest proportion of hemispheric electrical activity prior to ICP elevation. In the remaining patients, the percent reduction of SSEP activity after peak ICP levels was not statistically different from the percent reduction in SSEP activity prior to the peak ICP levels (p = .9). This data suggests that in a select group of patients with severe head injury, ICP does not cause SSEP deterioration, but rather is the consequence of deterioration of brain function.

Cerebral Oxidative Metabolism and Evoked Potential Deterioration after Severe Brain Injury: New Evidence of Early Posttraumatic Ischemia

BACKGROUND We commonly observe progressive deterioration in somatosensory evoked potentials (SSEPs) after severe head injury. We had previously been unable to relate this deterioration to raised intracranial pressure but had noted a relationship with decreasing transcranial oxygen extraction (arteriovenous oxygen difference [AVDO2]). The purpose of this study was twofold: to prove the hypothesis that deterioration in SSEP values is associated with decreasing AVDO2 and to test the subsidiary hypotheses that deteriorating SSEPs were the result of either ischemia/reperfusion injury or failure of oxygen extraction/utilization. METHODS Monitoring of 97 patients with severe traumatic brain injury (Glasgow Coma Scale scores of < or = 8 after resuscitation) included twice daily AVDO2 measurement and hourly SSEP recording for an average of 5 days. The last 51 patients also underwent 12-hourly measurement of cerebral blood flow (CBF), with calculation of the cerebral metabolic rate of oxygen. Cluster analysis was used to classify patients based on initial AVDO2 values and subsequent SSEP trends. The time courses of CBF, SSEPs, AVDO2, and cerebral metabolic rate of oxygen were examined in the groups defined by the cluster analysis. The clinical outcomes considered were survival or nonsurvival and the Glasgow Outcome Scale scores obtained at 3 months or more after injury. RESULTS Cluster analysis confirmed the association between high initial AVDO2 values and subsequent SSEP deterioration. Patients in this category initially had significantly higher AVDO2, lower CBF, and higher cerebral metabolic rates of oxygen but recovered to adequate levels within 24 to 36 hours after injury. SSEP values were initially identical in the patients with normal AVDO2 values and those with elevated AVDO2 but differed significantly at 60 hours after injury and beyond. CONCLUSION The findings of increased oxygen utilization and lowered CBF in the patients with deteriorating SSEPs strongly imply that early ischemia rather than failure of O2 extraction or utilization is responsible for the associated SSEP deterioration. This issue of defining thresholds for ischemia based on AVDO2 is confounded by the dependency of CBF and AVDO2 values on the time after injury.

Electrophysiologic assessment of intracerebral contusions in closed head injury

To determine whether intracerebral contusions should be evacuated in severe closed head injuries, patients with Glasgow Coma Scale scores < or = 8 and with radiologic evidence of midline shift on computed tomography admitted from 1987 through 1993 to our intensive care unit were monitored with median nerve somatosensory evoked potentials (SSEPs). A total of 44 patients and 84 hemispheres were included in the study. Initial SSEPs, calculated by a quantitative peak-peak amplitude method, were not significantly different between hemispheres that contained localized contusions > or = 2.5 cm, those that had evidence of diffuse injury or punctate lesions < 2.5 cm not considered suitable for surgical evacuation, and those without evidence of parenchymal hemorrhage (mean 14.64 microV, p = 0.43). The SSEPs deteriorated 41.2% from initial baseline levels in diffusely injured and 22.6% in contused hemispheres, whereas in normal-appearing hemispheres, SSEPs improved 51.1% (p = 0.01). The difference in SSEPs, however, was not significant between the contused and diffusely injured hemispheres. The results suggest that in severe closed head injury, cerebral hemispheres without radiologic evidence of structural damage have a high likelihood of improving after initial impact injury. Furthermore, hemispheres with localized contusions showed no more deterioration than those with more diffuse injury, implying that hemispheric electrical deterioration is not related to size of localized contusions but rather to underlying axonal damage. This indicates that surgical evacuation of localized contusions unless accompanied by mass effect is probably not warranted.

Petrous meningiomas: a review of seventeen cases.

Seventeen patients with petrous meningiomas managed at St. Michaels Hospital, during the years 1973-1987, were retrospectively reviewed. There were 15 females and 2 males; their ages ranged from 42 to 68 years (mean age: 53 years). The clinical presentation most commonly included headache and eighth cranial nerve dysfunction; the average duration of symptoms was 6 years (3 month-27 years). Computed tomography was performed in 15 cases. The mean tumour size was 2.5 centimeters (0.5-4 cm). The most common site of tumour origin was at or medial to the porus acousticus. Meningioma was suspected preoperatively in 10 of the 15 patients who had preoperative CT scans. Complete excision was obtained in 12 cases. There were no operative deaths after initial resections. Postoperative morbidity included worsening of pre-existing hearing loss in six patients, transient facial nerve palsies in six, permanent facial nerve palsies in four and new facial or corneal hypesthesia in three. Two patients developed cerebrospinal fluid fistulae. Tumour recurrence occurred into two patients in whom a complete resection was anticipated. Also, in two patients with incompletely resected tumours second operations were required. Fourteen patients are alive, 13 of whom care for themselves independently. The average follow-up was 5 years (6 months-9 years). It seems appropriate to recommend initial radical surgical excision of these benign tumours, where possible, in order to prevent tumour recurrence.

Medical Assistance in Dying (MAID) and the Neurosurgeon: Position Statement of the Canadian Neurosurgical Society (CNSS)

The Canadian Neurosurgical Society (CNSS) was established in 1965 to represent neurosurgeons nationally. The CNSS has approximately 300 members representing neurosurgeons and neurosurgery residents in Canada. The mission of the CNSS is to enhance the care of patients with diseases of the nervous system through education, advocacy, and improved methods of diagnosis, treatment, and rehabilitation. The CNSS is a member of the larger Canadian Neurological Sciences Federation, which represents the interests of patients encompassing the entire spectrum of neurological disease across the country. This position statement was generated by the CNSS subcommittee onMedical Assistance in Dying (MAID), consisting of the authors of this manuscript. In addition, the contents of the position statement were informed by a CNSS members’ survey on MAID (results to be published separately) as well as a CNSS members’ forum on MAID that took place at the annual CNSS meeting in Quebec City on June 21, 2016.