title: Are evoked potentials clinically useful in the study of patients with Chiari malformation Type 1?
abstract: OBJECTIVE In this study, the authors describe the brainstem auditory evoked potential (BAEP) and somatosensory evoked potential (SSEP) alterations found in a large cohort of patients with Chiari malformation Type 1 (CM-1), the relationship between the BAEPs/SSEPs and the clinical findings, the abnormalities in patients with associated syringomyelia, and the clinical and neuroradiological risk factors that are associated with abnormal evoked potentials (EPs). METHODS A prospectively collected database containing 545 patients with CM-1 was queried to search for patients satisfying the following criteria: 1) an age of at least 14 years, 2) neuroradiological criteria of CM-1, 3) no prior Chiari-related surgeries, and 4) preoperative EP studies conducted at the authors' institution. The 200 patients included in this cohort were classified into CM-0, CM-1, and CM-1.5 subtypes. Linear, planimetric, and angular measurements of the posterior fossa were conducted, as well as syringomyelia measurements. Two separate multiple logistic regression models were used, one to predict the covariates associated with abnormal BAEPs, and a second model to explore the variables associated with an abnormal SSEP. In these models, the BAEPs and SSEPs were dichotomized as being normal or abnormal. RESULTS Headaches were the main symptom in 70.5% of the patients, and Valsalva-induced headaches were most frequent in patients with CM-1 and CM-1.5 compared with patients with CM-0 (p = 0.031). BAEPs were abnormal in 38.5% of patients, and abnormal SSEPs were found in 43.5% of the entire cohort. Syringomyelia was most frequent in patients with CM-0 (64.3%) and CM-1 (51.1%) compared with those with CM-1.5 (34.7%; p = 0.03). Age (OR 1.03, 95% CI 1.00-1.06), the degree of tonsillar herniation (OR 1.08, 95% CI 1.01-1.16), and lower cranial nerve dysfunction (OR 3.99, 95% CI 1.29-14.01) had a statistically significant correlation with abnormal BAEPs. Only age (OR 1.07, 95% CI 1.04-1.10) and the degree of tonsillar herniation (OR 1.11, 95% CI 1.04-1.19) had a statistically significant correlation with abnormal SSEPs. CONCLUSIONS A high percentage of patients with CM-1 exhibited EP alterations regardless of their clinical or radiological findings. These findings suggest that EPs do not add any clinically relevant information nor are they helpful in establishing which symptomatic patients with CM should undergo surgical treatment. However, BAEP and SSEP studies clearly play an important role in incidentally detected patients with CM and may help to establish objective evidence of subclinical dysfunctions. In addition, neurophysiological studies may help to define subgroups of patients who require further testing and follow-up to personalize strategies for the management of incidental and oligosymptomatic patients.
authors.affiliation: Clinical Neurophysiology Department.|Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Spain.
authors.forename: Dulce
authors.initials: D
authors.lastname: Moncho
authors.affiliation: Neurosurgical Department, and.|Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Spain.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Poca
authors.affiliation: Clinical Neurophysiology Department.
authors.forename: Teresa
authors.initials: T
authors.lastname: Minoves
authors.affiliation: Clinical Neurophysiology Department.|Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Spain.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Ferré
authors.affiliation: Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Spain.
authors.forename: Victoria
authors.initials: V
authors.lastname: Cañas
authors.affiliation: Neurosurgical Department, and.|Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Sahuquillo
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001139:Arnold-Chiari Malformation / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology*; D015331:Cohort Studies; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D013595:Syringomyelia / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology; D055815:Young Adult
keywords: AP = anteroposterior; BAEP = brainstem auditory evoked potential; CM = Chiari malformation; CM-0 = CM Type 0; CM-1 = CM Type 1; CM-1.5 = CM Type 1.5; CVJ = craniovertebral junction; Chiari malformation; EP = evoked potential; FM = foramen magnum; IPL = interpeak latency; MN = median nerve; PF = posterior fossa; PFR = PF reconstruction; PTN = posterior tibial nerve; SCR = syringocord ratio; SSEP = somatosensory evoked potential; VB = vertebral body; brainstem auditory evoked potential; diagnostic and operative techniques; somatosensory evoked potential; syringomyelia