In vivo hippocampal glucose metabolism in mesial temporal lobe epilepsy.

BACKGROUND: The appearance of decreased 2-[(18)F]fluoro-2-deoxy-D-glucose (FDG) uptake in the mesial temporal region in temporal lobe epilepsy may simply reflect loss of gray matter due to hippocampal atrophy. Increased partial volume effects due to atrophic hippocampi may further increase appearance of hypometabolism. METHODS: The authors used a combination of MRI-PET coregistration, with MRI-based gray matter segmentation, and partial volume correction to improve the examination of hippocampal specific glucose uptake in FDG PET. The goal was to determine 1) if relative mesial temporal hypometabolism is an artifact of gray matter (hippocampal) atrophy, 2) whether hippocampal metabolism correlates with atrophy evaluated on MRI, and 3) if MRI-based partial volume correction influences measurement of hippocampal metabolic-volume relationships, including epilepsy lateralization. RESULTS: Findings showed that ipsilateral hippocampi of mesial temporal lobe epilepsy (MTLE) are relatively hypometabolic per unit of gray matter volume, and that hippocampal metabolism directly correlates with hippocampal volume. Specifically, partial volume corrected hippocampal metabolism correlated strongly (r = 0.613, p < 0.001) with hippocampal volume. Without partial volume correction, a weaker, but still significant, correlation was present (r = 0.482, p < 0.001). Degree of asymmetry was consistently greater and provided higher sensitivity of lateralization with partial volume vs non-partial volume corrected metabolic measurements. CONCLUSIONS: Although, decreased metabolism may occur in the absence of neuronal cell loss, hippocampal atrophy and presumed degree of neuronal cell loss appears to be a primary factor involved in the cause of decreased metabolism in epileptogenic hippocampi. Partial volume correction is recommended for optimal interpretation of hippocampal structure and function relationships.

Percutaneous management of abscess and fistula following pancreaticoduodenectomy.

PURPOSE: To evaluate the efficacy of percutaneous drainage of fluid collections following pancreaticoduodenectomy (Whipple's procedure). METHODS: We performed a retrospective review of 19 patients referred to our service with fluid collections following pancreaticoduodenectomy. The presence of associated enteric or biliary fistulas, the route(s) of access for image-guided drainage, the incidence of positive bacterial cultures, and the duration and success of percutaneous management were recorded. RESULTS: Fistulous communication to the jejunum in the region of the pancreatico-jejunal anastomosis was demonstrable in all 19 patients by gentle contrast injection into drainage tubes. Three patients had concurrent biliary fistulas. In 18 of 19 patients, fluid samples yielded positive bacterial cultures. Successful percutaneous evacuation of fluid was achieved in 17 of 19 patients (89%). The mean duration of drainage was 31 days. CONCLUSION: Percutaneous drainage of abscess following pancreaticoduodenectomy is effective in virtually all patients despite the coexistence of enteric and biliary fistulas.

Metastatic head and neck cancer: role and usefulness of FDG PET in locating occult primary tumors.

PURPOSE: To assess the usefulness of 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) of the head and neck in locating occult primary lesions in patients with metastatic cervical adenopathy. MATERIALS AND METHODS: Seventeen patients with metastatic cervical adenopathy of unknown primary origin were referred for FDG PET of the head and neck. All patients had undergone correlative anatomic imaging within 1 month of FDG PET. Surgical, clinical, and histopathologic findings were used to assess the performance of FDG PET. RESULTS: Increased apical lung uptake at FDG PET led to a biopsy-proved diagnosis of primary lung cancer in two patients. Of the remaining 15 patients, 10 had a focus of increased activity; directed biopsy of these sites led to confirmation of a primary carcinoma in seven patients. Correlative anatomic imaging failed to demonstrate the primary sites of disease in two of these seven patients. None of the five patients with negative FDG PET studies have manifested evidence of a primary site of disease during follow-up of 8-42 months (mean, 29 months). CONCLUSION: FDG PET allows effective localization of the unknown primary site of origin in metastatic head and neck cancer and can contribute substantially to patient care.

Clinical utility of positron emission tomography with 18F-fluorodeoxyglucose in detecting residual/recurrent squamous cell carcinoma of the head and neck.

PURPOSE: The use of positron emission tomography with 18F-fluorodeoxyglucose (FDG-PET) to detect residual/recurrent squamous cell carcinoma of the head and neck has been tested only in small groups of patients. Our purpose, therefore, was to evaluate the ability of this technique to detect the presence of tumor at both primary and nodal sites in a large cohort of patients. METHODS: All patients referred for PET scanning over a 2.5-year period with a question of residual or recurrent squamous cell carcinoma of the head and neck were identified. Thirty-five of 44 patients had sufficient follow-up to be meaningful to our analysis (range, 6-33 months). PET scans were interpreted visually with knowledge of the clinical history and correlative anatomic imaging findings. Detection of disease involving primary and nodal sites was assessed independently. Additionally, because each patient had been referred in an attempt to resolve a specific clinical problem, the usefulness of PET in accurately addressing these questions was assessed. RESULTS: At the primary site, sensitivity and specificity for residual/recurrent disease were 100% and 64%, respectively; for nodal disease, sensitivity and specificity were 93% and 77%, respectively. In helping to resolve the clinical question being asked, the positive predictive value of the test result was 65% and the negative predictive value was 91%. CONCLUSION: The high sensitivity and negative predictive value of PET scanning in our cohort of patients suggest an important role for this technique in the care of patients with suspected residual/recurrent head and neck carcinoma. The lower figures obtained for specificity and positive predictive value reflect the fact that increased FDG uptake may be due to either tumor or inflammation.

Endogenous adenosine is an autacoid feedback inhibitor of chloride transport in the shark rectal gland.

The present studies define the physiologic role of endogenous adenosine in the perfused shark rectal gland, a model epithelia for hormone-stimulated chloride transport. Chloride ion secretion, and venous adenosine and inosine concentrations increased in parallel in response to hormone stimulation. From a basal rate of 157 +/- 26 mu eq/h per g, chloride secretion increased to 836 +/- 96 and 2170 +/- 358 with 1 and 10 microM forskolin, venous adenosine increased from 5.0 +/- 1 to 126 +/- 29 and 896 +/- 181 nM, and inosine increased from 30 +/- 9 to 349 +/- 77 and 1719 +/- 454 nM (all P less than 0.01). Nitrobenzylthioinosine (NBTI), a nucleoside transport inhibitor, completely blocked the release of adenosine and inosine. Inhibition of chloride transport with bumetanide, an inhibitor of the Na+/K+/2Cl- cotransporter, or ouabain, an inhibitor of Na+/K+ ATPase activity, reduced venous adenosine and inosine to basal values. When the interaction of endogenous adenosine with extracellular receptors was prevented by adenosine deaminase, NBTI, or 8-phenyltheophylline, the chloride transport response to secretagogues increased by 1.7-2.3-fold. These studies demonstrate that endogenous adenosine is released in response to hormone-stimulated cellular work and acts at A1 adenosine receptors as a feedback inhibitor of chloride transport.

The natural history of epistaxis in hereditary hemorrhagic telangiectasia.

The purpose of this retrospective study is to document the natural history of epistaxis in patients with hereditary hemorrhagic telangiectasia. A telephone questionnaire was administered to 73 patients who had been previously screened for pulmonary arteriovenous malformations (PAVMs). The incidence of epistaxis in this population was 93%, with a mean onset age of epistaxis of 12 years, a mean frequency of bleeding of 18 episodes per month, and a mean duration of bleeding of 7.5 minutes. More than 90% of patients experienced the onset of epistaxis before the age of 21 and symptoms were progressive with age. There were no differences in the age of onset, frequency of epistaxis, or duration of epistaxis between patients with PAVMs versus those without PAVMs. Although the natural history of epistaxis does not predict the presence or absence of pulmonary arteriovenous malformations, epistaxis is an early marker of the disease, hereditary hemorrhagic telangiectasia, and might guide screening for pulmonary and cerebral arteriovenous malformations in children of affected parents.