Littoral sediment arsenic concentrations predict arsenic trophic transfer and human health risk in contaminated lakes.

Lake sediments store metal contaminants from historic pesticide and herbicide use and mining operations. Historical regional smelter operations in the Puget Sound lowlands have resulted in arsenic concentrations exceeding 200 µg As g-1 in urban lake sediments. Prior research has elucidated how sediment oxygen demand, warmer sediment temperatures, and alternating stratification and convective mixing in shallow lakes results in higher concentrations of arsenic in aquatic organisms when compared to deeper, seasonally stratified lakes with similar levels of arsenic pollution in profundal sediments. In this study we examine the trophic pathways for arsenic transfer through the aquatic food web of urban lakes in the Puget Sound lowlands, measuring C and N isotopes-to determine resource usage and trophic level-and total and inorganic arsenic in primary producers and primary and secondary consumers. Our results show higher levels of arsenic in periphyton than in other primary producers, and higher concentrations in snails than zooplankton or insect macroinvertebrates. In shallow lakes arsenic concentrations in littoral sediment are similar to deep profundal sediments due to arsenic remobilization, mixing, and redeposition, resulting in direct arsenic exposure to littoral benthic organisms such as periphyton and snails. The influence of littoral sediment on determining arsenic trophic transfer is evidenced by our results which show significant correlations between total arsenic in littoral sediment and total arsenic in periphyton, phytoplankton, zooplankton, snails, and fish across multiple lakes. We also found a consistent relationship between percent inorganic arsenic and trophic level (determined by δ15N) in lakes with different depths and mixing regimes. Cumulatively, these results combine to provide a strong empirical relationship between littoral sediment arsenic levels and inorganic arsenic in edible species that can be used to screen lakes for potential human health risk using an easy, inexpensive sampling and analysis method.

Human health risk from consumption of aquatic species in arsenic-contaminated shallow urban lakes.

Arsenic (As) causes cancer and non-cancer health effects in humans. Previous research revealed As concentrations over 200 µg g-1 in lake sediments in the south-central Puget Sound region affected by the former ASARCO copper smelter in Ruston, WA, and significant bioaccumulation of As in plankton in shallow lakes. Enhanced uptake occurs during summertime stratification and near-bottom anoxia when As is mobilized from sediments. Periodic mixing events in shallow lakes allow dissolved As to mix into oxygenated waters and littoral zones where biota reside. We quantify As concentrations and associated health risks in human-consumed tissues of sunfish [pumpkinseed (Lepomis gibbosus) and bluegill (Lepomis macrochirus)], crayfish [signal (Pacifastacus leniusculus) and red swamp (Procambarus clarkii)], and snails [Chinese mystery (Bellamya chinensis)] from lakes representing a gradient of As contamination and differing mixing regimes. In three shallow lakes with a range of arsenic in profundal sediments (20 to 206 µg As g-1), mean arsenic concentrations ranged from 2.9 to 46.4 µg g-1 in snails, 2.6 to 13.9 µg g-1 in crayfish, and 0.07 to 0.61 µg g-1 in sunfish. Comparatively, organisms in the deep, contaminated lake (208 µg g-1 in profundal sediments) averaged 11.8 µg g-1 in snails and 0.06 µg g-1 in sunfish. Using inorganic As concentrations, we calculated that consuming aquatic species from the most As-contaminated shallow lake resulted in 4-10 times greater health risks compared to the deep lake with the same arsenic concentrations in profundal sediments. We show that dynamics in shallow, polymictic lakes can result in greater As bioavailability compared to deeper, seasonally stratified lakes. Arsenic in oxygenated waters and littoral sediments was more indicative of exposure to aquatic species than profundal sediments, and therefore we recommend that sampling methods focus on these shallow zones to better indicate the potential for uptake into organisms and human health risk.

Gamma knife surgery for hypothalamic hamartomas accompanied by medically intractable epilepsy and precocious puberty: experience in Mexico.

OBJECT: Hypothalamic hamartoma is a nonneoplastic malformative mass of neurons and glia in the region of the hypothalamus. Because of its location, open surgery is associated with high morbidity and mortality rates. Gamma knife surgery (GKS) may be an efficient and safe treatment approach, which produces little morbidity. The authors describe the results of GKS in three patients with hypothalamic hamartomas. METHODS: All patients were male, aged 3, 12, and 15 years. The lesions were classified according to the Valdueza scale: one was Type IIb and two were Type IIa. The patients presented with gelastic seizures (15-20 per day), generalized epilepsy, behavioral abnormalities, and alterations of the sleep cycle. Precocious puberty was present in one patient. The Type IIb tumor had a volume of 1.8 cm3, and the Type IIa tumors were 597 mm3 and 530.1 mm3. The lesions received 12.5 Gy, 14 Gy, and 15 Gy, respectively, to the 50% isodose line. The patients were followed for 30 to 50 months. After 3 months, all patients showed improvement of their sleep, behavior, and epilepsy. At the present time, these patients are receiving low-dose antiepileptic agents and have achieved adequate social development and school integration. CONCLUSIONS: Gamma knife surgery appears to be a good, safe, and effective option for the treatment of selected hypothalamic hamartomas. No morbidity or mortality was associated with these three cases.

Trans-supraorbital approach to supratentorial aneurysms.

OBJECTIVE: The trans-supraorbital approach has the advantage of combining the keyhole principle with cranial base surgery. The anatomic fields that can be visualized with the use of this procedure have been demonstrated in cadavers, and the advantages and potential surgical applications of this procedure are described in this report. This article is the first to describe a group of intracranial supratentorial aneurysms. METHODS: We used the trans-supraorbital approach in 22 cases of supratentorial aneurysms. In this technique, an incision is made through the eyebrow, then a 3.5-cm craniotomy is performed with en bloc extension to the orbital arch, complemented by different drilling extensions of the orbital roof according to the surgical objective. We describe the anatomic details of the experimental work as well as the clinical results. RESULTS: The trans-supraorbital technique offers an unlimited wide exposure of neurovascular structures in this microsurgical corridor. The craniotomy extension allows greater exposure than the conventional keyhole supraorbital approach, which makes the technique safe for the patient and comfortable for the surgeon. All patient outcomes were successful; no serious complications from the surgical technique occurred. Our success was achieved through better microscopic illumination in the deep field and by gaining access to the complete supratentorial vascular territory with minimal cerebral retraction and an acceptable cosmetic result. CONCLUSION: The trans-supraorbital approach is effective for gaining access to and treating supratentorial aneurysms. Also, the microsurgical field is more convenient in microscope-assisted surgery because total reliance on the endoscope is not required, and minimal brain retraction is needed. This modification of the keyhole procedure also provides multiple surgical options in this microsurgical corridor, using the principles of minimal invasiveness in cranial base surgery.

Multimodal management of craniopharyngiomas: neuroendoscopy, microsurgery, and radiosurgery.

OBJECT: The goal of this study was to examine the role of gamma knife radiosurgery (GKS) and adjuvant neuroendoscopic procedures by assessing the outcome in 10 patients with craniopharyngiomas who were treated between 1998 and 2001. METHODS: In 10 consecutive patients (six males and four females, mean age 12 years [range 7-32 years]), there were nine mixed and one solid craniopharyngioma. In the last three cases, neuroendoscopic procedures were conducted. Two cases required insertion of an Ommaya reservoir. In another case partial removal of the cyst wall was performed using an endoscope to create a communication with the cerebrospinal pathways and thereby preclude the need for shunt insertion. CONCLUSIONS: Multimodal management of craniopharyngiomas seems to provide a better rate of survival and greater long-term disease control. It is suggested that GKS combined with adjuvant neuroendoscopy should be used as an alternative in treating recurrent or residual craniopharyngiomas if additional microsurgical removal cannot guarantee a cure.