Introduction
Spinal stenosis is a narrowing of the spinal canal and neural foramina. Symptoms, like back and/or leg radicular pain, are thought to result from neurologic compression and diminished local nerve perfusion. Case series and reports suggest that undiagnosed spinal stenosis could be a significant contributor to neurologic complications after neuraxial block. 

Case report
90-year-old woman presented for closed reduction of right proximal femoral fracture. Medical history of hypertension, congestive heart failure and chronic renal failure. A continuous spinal technique was performed using 2ml of an anesthetic mixture with 5mg of levobupivacaine, 2,5ug of sufentanil and 50mg of magnesium sulfate (MgSO4-). 40 minutes later she was admitted in the Postanaesthetic Care Unit, with complete reversal of motor and sensitive blockade. For control of pain (7/10) 1ml of levobupivacaine was administered through the subarachnoid catheter with immediate pain relief. After a few minutes, a motor block, disproportionate to the sensitive block, was noted. Four hours later as the motor block remained an urgent MRI was requested, revealing critical L2-L5 spinal stenosis and a small air bubble at L2 level. After evaluation by neurosurgery a conservative approach was decided. Complete recovery of quadriceps femoris function occurred 48 hours later, with no other neurological disfunction.

Discussion
Patients with spinal canal pathology, including spinal stenosis, are usually not candidates for neuraxial blockade because of the risk of exacerbating preexisting neurologic deficits or developing new ones. 
Although other causes such as ischemia or neurotoxicity cannot be ruled out, the most probable explanation for prolonged motor block in this case was the small pneumocephalus aggravating the previous neural compression. 

Conclusion
The safety of neuraxial anesthesia in patients with spinal stenosis remains controversial. Additional research is required to quantify the risk and characterize the mechanism of severe neurologic complications after spinal blockade. A double-crush mechanism should always be kept in mind when considering a spinal technique in patients with preexisting spinal stenosis. 


08 / Spinal stenosis: little air, big trouble