Sales slumped and net losses grew during the third quarter for NeuroMetrix Inc., as hospitals kept less of its nerve testing consumables on hand.

The Waltham, Mass.-based company posted sales of $6.3 million during the three months ended Sept. 30, down 10.6 percent compared with $7.1 million during the same period last year. Net losses widened 18 percent to $9.3 million, compared with $7.9 million during the third quarter of 2008.

But CFO Thomas Higgins — whom the company wooed from Caliper Life Sciences to be its own finance chief — told MassDevice that the bulk of the net loss was due to a one-time, $7.4 million accounting charge on the valuation of warrants related to a $17.3 million private equity placement during the quarter.

Absent that charge, Higgins said, net losses were $1.9 million for the quarter, an improvement of about 75 percent compared with the third quarter last year.

Most of NeuroMetrix’s revenues — 88.5 percent during the just-ended quarter — come from sales of the electrodes and needles used with its nerve-testing equipment. Those sales were down nearly 16 percent to $5.6 million during Q3 2009. The company blamed “seasonality and a decline in customer inventory replenishment likely due to overall economic conditions and healthcare uncertainty” for the decline.

Higgins also cited 510(k) clearance from the Food & Drug Administration for a component of NeuroMetrix’s Ascend device, which is used to verify the placement of drug-delivery needles near nerves. Higgins said the company expects to win clearance for the entire device and send it into the marketplace next year.

And he noted that the Centers for Medicare and Medicaid added a new reimbursement code for the type of nerve conduction tests the company’s equipment provides, at about 475 per limb tested.