title: Does a paresthesia during spinal needle insertion indicate intrathecal needle placement?
abstract: OBJECTIVE
  Paresthesias are relatively common during spinal needle insertion, however, the clinical significance of the paresthesia is unknown. A paresthesia may result from needle-to-nerve contact with a spinal nerve in the epidural space, or, with far lateral needle placement, may result from contact with a spinal nerve within the intervertebral foramen. However, it is also possible and perhaps more likely, that paresthesias occur when the spinal needle contacts a spinal nerve root within the subarachnoid space. This study was designed to test this latter hypothesis.
  
  
  METHODS
  Patients (n = 104) scheduled for surgery under spinal anesthesia were observed during spinal needle insertion. If a paresthesia occurred, the needle was fixed in place and the stylet removed to observe whether cerebrospinal fluid (CSF) flowed from the hub. The presence of CSF was considered proof that the needle had entered the subarachnoid space.
  
  
  RESULTS
  Paresthesias occurred in 14/103 (13.6%) of patients; 1 patient experienced a paresthesia twice. All paresthesias were transient. Following a paresthesia, CSF was observed in the needle hub 86.7% (13/15) of the time.
  
  
  CONCLUSIONS
  Our data suggest that the majority of transient paresthesias occur when the spinal needle enters the subarachnoid space and contacts a spinal nerve root. Therefore, when transient paresthesias occur during spinal needle placement it is appropriate to stop and assess for the presence of CSF in the needle hub, rather than withdraw and redirect the spinal needle away from the side of the paresthesia as some authors have suggested.
authors.affiliation: Department of Anesthesiology, Virginia Mason Medical Center, Seattle, WA 98101-2756, USA.
authors.forename: Ryan P
authors.initials: RP
authors.lastname: Pong
authors.forename: Benjamin S
authors.initials: BS
authors.lastname: Gmelch
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Bernards
mesh_terms: D000368:Aged; D000775:Anesthesia, Spinal; D000779:Anesthetics, Local / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D007278:Injections, Spinal / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D010292:Paresthesia / Q000134:cerebrospinal fluid / Q000209:etiology*; D011446:Prospective Studies; D013126:Spinal Nerve Roots / Q000502:physiology; D013346:Subarachnoid Space
chemical_list: D000779:Anesthetics, Local