Pathophysiology of altered consciousness during seizures: Subtraction SPECT study

BACKGROUND

The mechanisms underlying altered consciousness during seizures are poorly understood. Previous clinicopathologic studies suggest a role for the thalamus and upper brainstem in consciousness mechanisms.

OBJECTIVE

To examine blood flow changes associated with altered consciousness during seizures.

METHODS

Seventy-one patients with epilepsy who underwent video-EEG monitoring and ictal/interictal SPECT were studied. Patients were divided into three groups depending on their conscious state during seizures: 1) complete impairment of consciousness (CI), 2) no impairment of consciousness (NI), or 3) uncertain impairment of consciousness (UI). The distribution of blood flow changes during these seizures was assessed by subtraction (ictal - interictal) SPECT co-registered to MRI. Conscious state was assessed in relation to secondary ictal hyperperfusion in subcortical regions (i.e., thalamus and upper brainstem).

RESULTS

Impairment of consciousness showed a strong association with secondary hyperperfusion in the thalamic/upper brainstem region (p = 0.01), occurring in 92% (45/49) of CI, 69% (9/13) of UI, and 11% (1/9) of NI.

CONCLUSIONS

These findings are consistent with a role for the thalamus and upper brainstem in consciousness mechanisms. The authors suggest that the spread of epileptic discharges or a trans-synaptic activation (diaschisis) of these structures is an important mechanism in the alteration of consciousness during seizures. Variance in the results may be due to differences in timing of radioisotope injection, sensitivity of the subtraction SPECT technique, and the ability to clinically assess the conscious state.

Defining a future role for radiogenic therapy

The goal of cancer therapy is to eliminate the cancer and/or to arrest further growth while decreasing normal tissue toxicity, i.e. to increase the therapeutic ratio. This review focuses on a group of therapeutics that are either (1) directly stimulated by radiation to produce either directly or indirectly cytotoxic agents (i.e. genes under the control of a radiation inducible promoter that produce a cytotoxic protein or an enzyme that converts a prodrug to an active form, respectively); (2) auger-electron emitting radiolabelled oligonucleotides, antibodies, nucleotide analogues, or other small molecules that are internalized; (3) radiation inducible genes that produce a ligand or transporter (or the like) which then can be targeted by cytotoxic agents (e.g. radiolabelled substance). We have termed this group of therapeutics radiogenic therapy.

Thallium-201 scintigraphy after surgical repair of hemodynamically significant primary coronary artery anomalies

Nine patients with hemodynamically significant congenital coronary artery anomalies underwent surgical repair at our institution during the period 1960 to 1979. Four received diagnoses of anomalous left coronary artery arising from the pulmonary artery, while five patients had coronary artery fistulae. Stress 201Tl scintigraphy was performed on these patients 0.5 to 18 years after surgical correction as a means of assessing the adequacy of myocardial perfusion. No perfusion defects were visualized on any of the thallium studies. The surgical procedure used did not appear to influence the results of 201Tl stress imaging. Thus, these nine patients with surgically corrected primary coronary artery anomalies had no evidence of ischemia as assessed by stress thallium scintigraphy. Serial preoperative and postoperative thallium studies are now indicated to determine the role of this procedure in the management of hemodynamically significant congenital coronary artery anomalies.

Esophageal emptying in achalasia quantitated by a radioisotope technique

Delayed esophageal emptying of a radiolabeled meal distinguished symptomatic achalasia patients from asymptomatic controls. Esophageal emptying of the isotope meal significantly improved in ten achalasia patients after pneumatic dilation, and in one patient after surgical myotomy. The emptying curve in some patients after treatment simulated that of control subjects. Quantitation of esophageal emptying by a radiolabeled meal is a physiologic test that may be useful in evaluating results of therapy for achalasia.

Solitary abnormalities in bone scans of patients with extraosseous malignancies

The incidence and significance of solitary bone scan abnormalities were assessed in a study of 1,129 consecutive patients with extraskeletal primary malignancies. Solitary abnormalities were encountered in 172 cases (15%). The etiology of the scan abnormality was established in 90 of the 172 cases; 58 (64%) were due to metastatic disease, and 32 (36%) were secondary to a benign process. A significant percentage of solitary scan abnormalities is due to benign disease processes, even in patients with proved extraosseous malignancies.

Body-background defects with 99mTc-DTPA after renal transplantation: case reports

Photon-deficient areas adjacent to transplanted kidneys were seen in the early phases of several dynamic studies obtained with 99mTc-diethylenetri-aminepentaacetic acid (99mTc-DTPA). The causes included hematoma, urinoma, and lymphocele. These fluid collections do not readily exchange as part of the extracellular space and, if sufficiently large, may be visualized as photon-deficient areas in the normally homogeneous background of 99mTc-DTPA studies.