The use of magnetic resonance imaging in exertional compartment syndromes

This prospective, double-blind study was carried out to assess the usefulness of magnetic resonance imaging (MRI) as a noninvasive method in the diagnosis of chronic compartment syndrome (CCS). As well, a new radiopharmaceutical known as methoxy isobutyl isonitrile that has been shown to be taken up by muscle in direct proportion to its blood flow was used to illustrate the possible pathophysiology of this syndrome. Twenty patients with a history of chronic leg pain and possible diagnosis of CCS and five normal volunteers had preexercise and postexercise MRI, nuclear medicine imaging, and static and dynamic slit catheter pressure studies. Nine patients had classic symptoms; only five of these nine had abnormal pressure studies. The other 11 patients had an element of pain at rest and had normal pressure studies. The nuclear blood flow studies were normal in all 25 legs tested in this study. Measurement of intrinsic MRI parameters T1 and T2 in the normal legs as well as in those with an atypical history showed a marked elevation with exercise and a gradual return to baseline postexercise that was similar to the pressure curves. In the five patients with a clinical history and elevated pressures, four had abnormal MRI studies with failure of T1 to return to baseline values. Although these results demonstrate the potential of MRI as a tool for noninvasively monitoring muscle status, clinical history and examination remain important in the diagnosis of CCS. This study indicates that the pathophysiology of exertional compartment syndrome does not appear to be related to ischemia.

Naloxone and morphine inhibit gastric emptying of solids

Gastric emptying studies were performed on six healthy volunteers using a radioisotope test meal. Each subject was studied three times (control, morphine 7.5 mg, naloxone 2 mg). Both intravenous morphine and intravenous naloxone significantly delayed gastric emptying when compared with the control study. These results suggest that opiate receptors, opiate neurones, and enkephalin may regulate gastric motility and that under certain circumstances naloxone may act as an opiate agonist.

Complementary roles of low-dose SPECT-CT and high-resolution volume CT for detection of coronary artery disease

A 70-year-old woman with a high pretest likelihood of coronary artery disease (CAD) underwent a Tc-99m MIBI SPECT-CT study for myocardial perfusion imaging (MPI), which was complemented by a high-resolution volume CT (VCT) study. After attenuation correction, an MPI pattern of ischemia was detected in the lateral wall of the myocardium. The CT calcium score (CTCS) was above the 75th percentile. The CT angiography (CTA) demonstrated a 70% stenosis at the ostial part of the circumflex artery, and incidentally revealed a saccular aneurysm. In today's nuclear cardiology, low-dose SPECT-CT plus high-resolution VCT allows anatofunctional assessment of suspected CAD.

Utility of Ictal SPECT in the Presurgical Evaluation of Rasmussen's Encephalitis

BACKGROUND

Rasmussen's encephalitis is a progressive disease characterized by severe progressive neurological and cognitive deficits. It is a difficult condition to treat with conventional medical treatment and requires, in most of the cases, surgical intervention.

METHODS

We present the case of a patient with Rasmussen's encephalitis who presented with epilepsia partialis continua, who did not respond to antiepileptic treatment and was evaluated for possible surgical intervention.

RESULTS

The electroencephalographic studies revealed bihemispheric involvement during seizures, although magnetic resonance imaging (MRI) showed a marked right hemispheric atrophy. Hyperperfusion over the right hemisphere was seen with the performance of ictal single photon emission computed tomography (SPECT), which finally guided a right functional hemispherectomy and subsequent seizure control.

CONCLUSION

Ictal SPECT could be a useful tool in the armamentarium of tools used for the localization of the epileptogenic focus in patients with Rasmussen's encephalitis and other localization-related epilepsies.

Evaluating the Development of a SPECT Protocol in a Canadian Epilepsy Unit

Background:

Functional neuroimaging can address some challenges of seizure localization, and sometimes preclude the need for EEG recording using intracranial electrodes. Ictal Single Photon Emission Computed Tomography (SPECT) has developed into an important tool in the presurgical evaluation of patients with medically-intractable localization-related epilepsy. The purpose of the study was to determine whether the development of a programme using trained nurses to perform ictal injections enabled a more efficient delivery of radiopharmaceuticals and therefore a greater sensitivity and specificity of outcome.

Methods:

In our epilepsy unit, nursing staff inject 99mTc-HMPAO at bedside, during or at seizure onset. Brain SPECT is performed later on a gamma camera.

Results:

Since the implementation of the new protocol (February 2005), 57 scans have been performed: 22 ictal and 35 interictal. Latency of ictal injection was found to be 5-40 seconds (mean 19.7 sec, standard deviation (SD) 10.4). Only 20% of reconstituted radiopharmaceutical vials were not used. Contamination rate was nil. Sixty three percent of SPECT studies were concordant with standard presurgical evaluation.

Conclusion:

The latency of injections and the percentage of unused vials indicated an efficient and effective protocol compared to the literature. Our results show that ictal SPECT can be a safe, noninvasive procedure performed on a routine basis in the epilepsy unit when appropriately trained support staff are incorporated into a structured multidisciplinary programme.

Radioaerosol ventilation imaging in ventilator-dependent patients. Technical considerations

The differentiation of pulmonary embolism (PE) from regional ventilatory abnormalities accompanied by reduced perfusion requires contemporary perfusion and ventilation studies. Distinguishing these conditions in ventilator-dependent patients is aided by administering a Tc-99m aerosol to characterize regional ventilation, and by performing a conventional Tc-99m MAA perfusion study. The technique uses a simple "in-house" constructed apparatus. Simple photographic techniques suffice, but computer subtraction of perfusion from the combined perfusion-ventilation image renders interpretation easier if aerosol administration follows perfusion imaging. Multiple defects can be examined in a single study. Excluding normal or near-normal perfusion studies, PE was thought to be present in eight of 16 patients after perfusion imaging alone, but in only one of eight after added aerosol imaging. Angiography confirmed the diagnosis in that patient. Of the eight patients who had abnormal perfusion but were thought unlikely to have PE from the perfusion study alone, two had normal ventilation, and subsequently were shown to have PE by angiography. Because angiography was only performed on patients who were thought to have a high probability of PE on sequential perfusion-ventilation imaging, the true incidence of PE may have been higher. Aerosol ventilation imaging is a useful adjunct to perfusion imaging in patients on ventilators. It requires an efficient delivery system, particularly if aerosol administration follows perfusion imaging, as it does in this study. The major disadvantage of aerosol imaging compared to a gas in intubated patients is the significant bronchial deposition due to retained mucus secretions.(ABSTRACT TRUNCATED AT 250 WORDS)