Abnormal Electrophysiological Findings Research Articles

Clozapine-induced stuttering in the absence of known risk factors: a case report

BackgroundStuttering is a rare side effect of clozapine. It has been shown to occur in the presence of one or more factors such as abnormal electrophysiological findings and seizures, extrapyramidal symptoms, brain pathology, and a family history of stuttering. Few case reports have documented the occurrence of clozapine-induced stuttering in the absence of these risk factors.Case presentationA 29-year-old African male on clozapine for treatment-resistant schizophrenia presented with stuttering at a dosage of 400 mg/day that resolved with dose reduction. Electroencephalogram findings were normal, and there was no clinical evidence of seizures. The patient had no prior history or family history of stuttering, had a normal neurological examination, and showed no signs of extrapyramidal symptoms.ConclusionClinicians ought to be aware of stuttering as a side effect of clozapine, even in the absence of known risk factors. Further research should investigate the pathophysiology of clozapine-induced stuttering.

Spinal accessory neuropathy in patients with chronic trapezius myofascial pain syndrome

BackgroundMyofascial pain syndrome is a common musculoskeletal problem affecting the trapezius muscle. The aim was to assess the presence of spinal accessory neuropathy in patients with unilateral chronic trapezius myofascial pain syndrome.ResultsThe study included 25 patients with unilateral chronic trapezius myofascial pain syndrome and 20 apparently healthy volunteers as the control group. There was a significantly delayed spinal accessory nerve latency on the symptomatic side in comparison to either asymptomatic side (P = 0.014) and control group (P = 0.001). Compound muscle action potential amplitude did not significantly differ between the symptomatic side versus the asymptomatic side and control group. Delayed spinal accessory nerve latency was present in seven patients (28%) and reduced compound muscle action potential amplitude in one of them (4%). The needle electromyography of the upper trapezius muscle revealed neuropathic motor units and incomplete interference pattern in the patient who showed reduced compound muscle action potential amplitude. Abnormal rest potentials were absent in all patients. Individually, seven patients (28%) had electrophysiological evidence of spinal accessory neuropathy, but only one (4%) of them had clinical evidence of spinal accessory neuropathy. Patients with abnormal electrophysiological findings had longer duration of complaint and more severe pain.ConclusionsSpinal accessory neuropathy is common among patients with chronic trapezius myofascial pain syndrome. It could contribute to increased pain severity of myofascial pain syndrome. Electrodiagnosis is a good modality for identifying subclinical spinal accessory neuropathy.

Evidence of central involvement in essential tremor: a detailed study of auditory pathway physiology.

Essential tremor (ET) is a common tremor disorder that is likely neurodegenerative. The pathophysiology of ET involves the cerebellum and its connections in the brainstem and thalamus. Hearing dysfunction has been shown to be a non-motor finding in ET patients. A limited number of studies have suggested that cochlear pathology is the cause, but studies have not evaluated the integrity of the primary auditory pathway in ET. The main aim of this study is to investigate the integrity of the auditory pathway via auditory brainstem response (ABR) and auditory middle latency response (AMLR), thereby allowing us to evaluate the auditory pathway from the 8th cranial nerve to the cerebral cortex. Sixteen ET patients and sixteen age- and gender-matched controls (64 ears) were evaluated. In the ABR study, we detected prolongation of wave V peak latencies (ms) in ET (p = 0.02). In the AMLR study, P0 (p = 0.03), Pa (p = 0.008), Na (p = 0.03), and Nb (p = 0.01) waves differed between the two groups. Eleven ET patients and four control subjects had abnormal electrophysiological findings (ABR or AMLR or both) (68.8% vs. 25%, p = 0.01). Tremor duration was greater in ET patients with abnormal electrophysiological findings (p = 0.01). Finally, we observed prolongation of latencies after the ABR III wave, indicating that abnormalities exist within the superior olivary complex. For the first time, our research provides evidence that ET-related pathology is present at the subcortical and cortical levels of the auditory pathway.

Glenohumeral Rotational Deficit and Suprascapular Neuropathy in the Hitting Shoulder in Male Collegiate Volleyball Players.

Repetitive overhead movements stress the dominant shoulder of volleyball players, potentially causing glenohumeral internal rotation deficit (GIRD) and suprascapular neuropathy. The aim of this study was to determine the prevalence of pathological GIRD and suprascapular neuropathy in male collegiate volleyball players. We evaluated 22 male collegiate volleyball players and compared the range of motion, the isometric shoulder strength, the thickness of the infraspinatus (ISP) muscle, and the latency and amplitude of the suprascapular nerve [in a nerve conduction study (NCS)] between the hitting and contralateral shoulders. Correlations between the physical findings and each parameter were also determined. The internal rotation angle of the hitting shoulder (55.1±8.7°) was significantly less than that of the contralateral shoulder (64.5±10.2°) (P<0.001); pathological GIRD (≥20°) was found in four players (18.2%). Three players (13.6%) showed abnormal electrophysiological findings of the suprascapular nerve on the ISP muscle in the hitting shoulder. The external-to-internal rotation (ER/IR) torque ratio in the hitting shoulder (99±18%) was significantly lower than that in the contralateral shoulder (106±12%) (P=0.04); no significant differences were observed in ISP muscle thickness or NCS data between the hitting and contralateral shoulders. The prevalence of pathological GIRD in male collegiate volleyball players was consistent with that of previous studies. Meanwhile, the prevalence of suprascapular neuropathy was less than that previously reported in high-level volleyball players. Preventive posterior rotator cuff strengthening programs are recommended to correct imbalances between ER and IR in the hitting shoulder, thereby decreasing the risk of shoulder injury.

Cystic Fibrosis.

Universal screening of newborn babies for cystic fibrosis was launched in Germany on 1 September 2016. Here we present up-to-date information on the diagnosis, treatment, and prognosis of this disease. This article is based on relevant publications retrieved by a selective search in PubMed, along with guidelines from Germany and abroad and systematic reviews. Cystic fibrosis is caused by a gene mutation leading to dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) protein. It affects multiple organ systems-the lungs, pancreas, upper airways, liver, intestine, and reproductive organs-to varying degrees. Its incidence among newborn babies in Germany is between 1 in 3300 and 1 in 4800. Its diagnosis requires both clinical evidence (positive newborn screening, sibling[s] with cystic fibrosis, clinical signs) and the demonstration of CFTR dysfunction by an elevated chloride concentration in sweat, and/or two disease-causing mutations, and/or abnormal electrophysiological findings (nasal potential difference measurement, intestinal short-circuit current measurement). Patients should be cared for by specialized cystic fibrosis centers in close cooperation with their primary care physicians. The median life span of patients with this disease has risen steadily to the current value of 40 years. Aside from symptomatic treatment, the first mutation- specific treatments have recently become available. Early diagnosis and optimized treatment prolong the lives of persons with cystic fibrosis and improve their quality of life. Causally directed treatment for all patients and their effects on the course of disease are now central issues for further research.

Uric acid levels correlate with the severity of diabetic sensorimotor polyneuropathy

IntroductionDiabetic sensorimotor polyneuropathy (DSP) is the most frequent complication in patients with diabetes mellitus (DM), and is associated with age, DM duration, and HbA1c levels. In addition, higher uric acid (UA) levels are reported in patients with DSP. ObjectivesTo explore whether UA levels correlate with DSP severity. MethodsWe extracted the demographic data, clinical history, neurological and electrophysiological examinations and laboratory findings of 115 patients diagnosed with DSP from January 2012 to December 2015. ResultsThe mean age of the total cohort was 62±13years, with 61% men. A positive correlation was demonstrated between uric acid levels and increasing sensory symptoms, and more abnormal electrophysiological findings and vibration perception thresholds. In addition, correlations with gait abnormality, the presence of paraproteinemia and creatine kinase levels were found. DiscussionOur study results show that uric acid levels correlate with clinical and electrophysiological severity of DSP, providing additional evidence for the relationship between the two, and a potential therapeutic target for DSP.

Prolonged Sinus Pauses upon Termination of Paroxysmal Atrial Fibrillation: Abnormal Right Atrial Electrophysiologic and Electroanatomic Findings.

The efficacy of pulmonary vein antral isolation for patients with prolonged sinus pauses (PSP) on termination of atrial fibrillation has been reported. We studied the right atrial (RA) electrophysiologic and electroanatomic characteristics in such patients. Forty patients underwent electroanatomic mapping of the RA: 13 had PSP (group A), 13 had no PSP (group B), and 14 had paroxysmal supraventricular tachycardia (control group C). Group A had longer P-wave durations in lead II than did groups B and C (115.5 ± 15.4 vs 99.5 ± 10.9 vs 96.5 ± 10.4 ms; P=0.001), and RA activation times (106.8 ± 13.8 vs 99 ± 8.7 vs 94.5 ± 9.1 s; P=0.02). Group A's PP intervals were longer during adenosine triphosphate testing before ablation (4.6 ± 2.3 vs 1.7 ± 0.6 vs 1.5 ± 1 s; P <0.001) and after ablation (4.7 ± 2.5 vs 2.2 ± 1.4 vs 1.6 ± 0.8 s; P <0.001), and group A had more complex electrograms (11.4% ± 5.4% vs 9.3% ± 1.6% vs 5.8% ± 1.6%; P <0.001). Compared with group C, group A had significantly longer corrected sinus node recovery times at a 400-ms pacing cycle length after ablation, larger RA volumes (100.1 ± 23.1 vs 83 ± 22.1 mL; P=0.04), and lower conduction velocities in the high posterior (0.87 ± 0.13 vs 1.02 ± 0.21 mm/ms; P=0.02) and high lateral RA (0.89 ± 0.2 vs 1.1 ± 0.35 mm/ms; P=0.04). We found that patients with PSP upon termination of atrial fibrillation have RA electrophysiologic and electroanatomic abnormalities that warrant post-ablation monitoring.

Rapid, Objective and Non-invasive Diagnosis of Sudomotor Dysfunction in Patients With Lower Extremity Dysesthesia: A Cross-Sectional Study.

ObjectiveTo determine whether patients with lumbosacral (LS) radiculopathy and peripheral polyneuropathy (PPNP) exhibit sudomotor abnormalities and whether SUDOSCAN (Impeto Medical, Paris, France) can complement nerve conduction study (NCS) and electromyography (EMG).MethodsOutpatients with lower extremity dysesthesia underwent electrophysiologic studies and SUDOSCAN. They were classified as normal (group A), LS radiculopathy (group B), or PPNP (group C). Pain severity was measured by the Michigan Neuropathy Screening Instrument (MNSI) and visual analogue scale (VAS). Demographic features, electrochemical skin conductance (ESC) values on hands and feet, and SUDOSCAN-risk scores were analyzed.ResultsThere were no statistical differences in MNSI and VAS among the three groups. Feet-ESC and hands-ESC values in group C were lower than group A and B. SUDOSCAN-risk score in group B and C was higher than group A. With a cut-off at 48 microSiemens of feet-ESC, PPNP was detected with 57.1% sensitivity and 94.2% specificity (area under the curve [AUC]=0.780; 95% confidence interval [CI], 0646–0.915). With a SUDOSCAN-risk score cut-off at 29%, NCS and EMG abnormalities related to LS radiculopathy and PPNP were detected with 64.1% sensitivity and 84.2% specificity (AUC=0.750; 95% CI, 0.674–0.886).ConclusionSUDOSCAN can discriminate outpatients with abnormal electrophysiological findings and sudomotor dysfunction. This technology may be a complementary tool to NCS and EMG in outpatients with lower extremity dysesthesia.

Perineal Neurophysiological Assessment in 23 Patients Suffering from Persistent Genital Arousal Disorders: Evidence of Pudendal Neuropathy?

ABSTRACTObjectives: Persistent genital arousal disorder (PGAD) is a rare condition. Our aim was to study whether or not the pudendal nerve is involved in PGAD, by means of electromyographic (EMG) testing. Methods: Twenty-three women who fulfilled the five criteria of PGAD were included in this study. After an in-depth interview and routine investigations, a perineal EMG assessment was performed. Concentric needle electromyography (EMG) testing with motor unit potential analysis of the pelvic floor muscles (bulbocavernosus muscle and striated external anal sphincter), study of the sacral reflex latency (SRL), and measurement of pudendal nerve terminal motor latency (PNTML) were performed. Results: Perineal ENMG demonstrated neurogenic changes in 14 (60.8%) of the patients. Denervation was found in all 14 patients with abnormal electrophysiological findings. Among them, 12 (85.7%) had altered PTNML and/or SRL. PTNML was delayed on the anal branch in 9 out of 14 (bilateral in 5 cases) and on the perineal branch in 9 out of 14 (bilateral in 6 cases). Conclusions: This study shows that pudendal neuropathy is frequent among women suffering from PGAD. However, due to the lack of a control group, involvement of pudendal neuropathy in the pathogenesis of PGAD remains unclear.

Increased proinflammatory cytokines in sera of patients with multifocal motor neuropathy

BackgroundMultifocal motor neuropathy (MMN) is characterized by clinical improvement with intravenous immunoglobulin and the frequent detection of anti-ganglioside antibodies. However, the immunological background of the neuronal damage in MMN is still unclear. ObjectiveThe aim of this study is to investigate abnormalities in the cytokine and chemokine profiles of MMN patients. MethodsSera from 16 patients with MMN, 16 patients with sporadic amyotrophic lateral sclerosis (ALS), and 15 patients with other non-inflammatory neurological diseases (ONDs) were analyzed for 27 cytokines and chemokines using a multiplex bead array. We also checked whether the altered cytokine/chemokine profile in the MMN group differed significantly in the presence or absence of abnormal electrophysiological findings. ResultsSerum IL-1Ra, IL-2, G-CSF, TNF-α, and TNFR1 levels were significantly higher in the MMN group than in the ONDs group. Of these, G-CSF and TNF-α also showed significant increases compared to the ALS group. Serum G-CSF and TNF-α levels were significantly higher in MMN patients presenting with focal demyelination including conduction block than in patients without any focal demyelination. ConclusionsProinflammatory cytokines may contribute to peripheral nerve demyelination in MMN.

Spinal Primitive Neuroectodermal Tumor Mimicking as Chronic Inflammatory Demyelination Polyneuropathy

We report a young boy who presented with progressive weakness of lower extremities associated with areflexia and abnormal electrophysiological findings initially suggestive of chronic inflammatory demyelinating polyneuropathy. Initial lumbosacral spinal magnetic resonance imaging (MRI) showed thickened descending spinal nerve roots only. Immunomodulating therapy was given but with limited clinical response. Repeated spine magnetic resonance imaging showed cauda equina and also new spinal cord extramedullary contrast enhancement. The initial extensive investigations including open biopsy did not point to any specific diagnosis. Only through pursuing a repeated biopsy, the diagnosis of the spinal peripheral primitive neuroectodermal tumor was confirmed. This case highlights the diagnostic challenges of the spinal peripheral primitive neuroectodermal tumor that could have an initial chronic inflammatory demyelinating polyneuropathy-like presentation. The literature review confirms that this is a rare condition and cauda equina origin has only been reported in adults and teenagers, and this is the first reported case in a young child.

Changes of the six-item carpal tunnel syndrome (CTS) symptoms scale and the nerve electrophysiological findings after surgery for CTS with abnormal nerve electrophysiological findings

Changes of the six-item carpal tunnel syndrome (CTS) symptoms scale and the nerve electrophysiological findings after surgery for CTS with abnormal nerve electrophysiological findings

Persistence of Abnormal Electrophysiological Findings after Carpal Tunnel Release

Practitioners may refer to experienced hand surgeons to differentiate a recurrence in carpal tunnel syndrome (CTS) from a failed carpal tunnel release. The patient may complain about the reappearance of symptoms, whatever is the cause. Nerve conduction studies (NCS) are often required by the practitioner to assist the final diagnosis. We observed abnormal values in NCS in patients who were clinically healed from CTS. We evaluated the changes preoperatively and, then, at 1, 3, 6, 9, and 12 month postoperatively. At the same time, we performed a retrospective study on a group of 37 clinically healed patients. Follow-up ranged from 2 to 20 years. Surgical treatment let the electrophysiological parameters to improve toward physiological values; however, normality is hardly ever reached. This sort of ''electrophysiological scar'' is true for all the parameters measured. In presence of CTS, the latency difference between the radial and median sensory nerve action potentials, recorded following thumb stimulation, produces a double peak shift. The ''double peak shift'' best described this ''electrophysiological scar,'' being a parameter that should measure about zero in the normal population. In conclusion, abnormal postoperative electrophysiological findings cannot substantiate the diagnosis of a poor outcome of a carpal tunnel release nor a recurrence of CTS.

Phrenic nerve palsy after internal jugular venous catheter placement

Central venous catheters are usually inserted to measure the central venous pressure or use as an administration route for fluid or medication. There are reports that complications, such as arterial puncture, pneumothorax, occur in approximately 15% of cases when inserting it [1,2]. Phrenic nerve palsy is a very rare complication attributed to central venous catheter insertion. It can be caused when inserting the catheter into the subclavian vein or internal jugular vein, as well as when venal puncture is attempted several times with a thick needle, and can also occur when the needle is inserted too deeply, directly injuring the nerves. We recently had a case of phrenic nerve palsy, which was discovered late and its cause suspected to be central venous catheter insertion. The patient, a 75 year old female, underwent left nephroureterectomy for papillary urothelial carcinoma. At the time, there were no abnormalities in the preoperative physical examinations and laboratory tests including a chest x-ray. A central venous catheter was inserted through land mark guidance, by means of the anterior approach, into the right internal jugular vein [1]. There were no difficulties or specific events during the procedure. The operation proceeded without any complications, yet the chest x-ray taken on the same day after the surgery, indicated pulmonary congestion and atelectasis on the right lower lobe. Two days after the surgery, the central venous catheter was removed. The ABGA, performed on the third day post surgery showed pH 7.42, PaCO2 40.7 mmHg, and PaO2 64.1 mmHg in room air and the chest x-ray showed no differences when compared to the one before. Ten days after the surgery, the patient was discharged with no specific symptoms and was advised to take deep breaths and cough. Six months later, the patient visited the outpatient clinic with dyspnea, which began occurring a month prior without any other symptoms, such as coughing or sputum. Atelectasis in the right lower lobe was observed in the chest x-ray taken, which was similar to the chest x-ray from six months before. In the dynamic chest CT, the right diaphragm had risen and segmental atelectasis could be observed in the right middle and lower lobes. Both an electroneurography and electromyography were performed on the right upper and lower limbs under the suspicion of phrenic nerve palsy. The results showed an abnormal electrophysiological finding that suggested right cervical radiculopathy (C 4, 5, 7) and right phrenic neuropathy. The right median nerve, ulnar nerve, lower limb nerve, and left phrenic nerve, were all normal. In the Jolly test performed, in order to rule out abnormalities in the neuromuscular junction, no abnormal electrophysiological findings were observed. The patient did not complain of other symptoms in the upper or lower limbs, other than dyspnea. Also, with the exception of the history of central venous catheter insertion six months prior, there were no other causes for the phrenic nerve palsy, such as tumor or infection. Hence, the central venous catheter insertion was suspected as the most probable cause for the phrenic nerve palsy. The patient complained of dyspnea continuously, so a diaphragm plication was performed. The pulmonary function test, performed nine days after the surgery, showed FVC 1,510 (67%) ml and FEV1 1,030 (68%) ml, which had improved from

Peripheral neuropathies in Sjögren syndrome: a new reappraisal

BackgroundThe prevalence of peripheral neuropathy in patients with Sjögren syndrome remains unclear owing to conflicting results in the published series, with numbers ranging from 2% to over 60% of Sjögren...

Mismatch negativity and adaptation measures of the late auditory evoked potential in cochlear implant users

A better understanding of the neural correlates of large variability in cochlear implant (CI) patients’ speech performance may allow us to find solutions to further improve CI benefits. The present study examined the mismatch negativity (MMN) and the adaptation of the late auditory evoked potential (LAEP) in 10 CI users. The speech syllable /da/ and 1-kHz tone burst were used to examine the LAEP adaptation. The amount of LAEP adaptation was calculated according to the averaged N1-P2 amplitude for the LAEPs evoked by the last 3 stimuli and the amplitude evoked by the first stimulus. For the MMN recordings, the standard stimulus (1-kHz tone) and the deviant stimulus (2-kHz tone) were presented in an oddball condition. Additionally, the deviants alone were presented in a control condition. The MMN was derived by subtracting the response to the deviants in the control condition from the oddball condition. Results showed that good CI performers displayed a more prominent LAEP adaptation than moderate-to-poor performers. Speech performance was significantly correlated to the amount of LAEP adaptation for the 1-kHz tone bursts. Good performers displayed large MMNs and moderate-to-poor performers had small or absent MMNs. The abnormal electrophysiological findings in moderate-to-poor performers suggest that long-term deafness may cause damage not only at the auditory cortical level, but also at the cognitive level.

Auditory testing profiles of Pelizaeus-Merzbacher disease.

To characterize the auditory manifestations of patients diagnosed with Pelizaeus-Merzbacher Disease (PMD), a rare X-linked disorder of myelin classically characterized by nystagmus, spastic quadriparesis, ataxia, and cognitive delay in early childhood or progressive disease in adulthood. A prospective case study of 5 pediatric and 3 adult patients diagnosed with PMD who demonstrate varying degrees of abnormal auditory function. These patients underwent comprehensive audiological evaluations (audiometry, tympanometry, otoacoustic emissions), auditory processing tests (Dichotic Listening, Frequency Pattern Test, Duration Pattern Test), and electrophysiological measures (Auditory Brainstem Response). Abnormal electrophysiological findings with normal cochlear function were found in all test subjects. Further testing completed on adult subjects revealed further central auditory dysfunction via auditory processing tests. All the adult test subjects had abnormal results on auditory processing tests including significant left ear deficits on dichotic digits and poor duration pattern test scores. Auditory processing test results indicated strong right ear advantages for all adult PMD test subjects in Dichotic Digit testing. The degree of audiological central dysfunction findings was more severe in subjects with greater symptoms of the disease. Our findings indicate the need for a full audiological test battery on all patients with Pelizaeus-Merzbacher disease and other severe neurological disorders.

The H reflex as a diagnostic tool for Miller Fisher syndrome in pediatric patients

Miller Fisher syndrome (MFS) is characterized by gait ataxia, external ophthalmoplegia and areflexia. Immunohistochemical studies suggest a pathophysiological role for anti-GQ1b antibodies at the paranodal regions of the oculomotor nerves, at some neurons of the dorsal root ganglia (DRG) and at motor nerve terminals. The variability of abnormal electrophysiological findings reported is significant. Nerve conduction studies, H reflex and F waves were performed in three pediatric patients with MFS. The H reflex was absent in all three patients. It was the sole abnormality in two patients whereas the third patient also had extended motor and sensory nerve conduction impairments. The transient character of this isolated absence has been confirmed in one patient. These data point to a proximal demyelinating process near the DRG. This may involve selective demyelination of Ia spinocerebellar afferent fibers originating in muscle spindles. In a pediatric practice, the H reflex seems to be a useful tool in the diagnostic approach to MFS.

Role of Ulnar Nerve Sonography in Leprosy Neuropathy With Electrophysiologic Correlation

The purpose of this study was to evaluate the diagnostic usefulness of ulnar nerve sonography in leprosy neuropathy with electrophysiologic correlation. Twenty-one consecutive patients with leprosy (12 men and 9 women; mean age +/- SD, 47.7 +/- 17.2 years) and 20 control participants (14 men and 6 women; mean age, 46.5 +/- 16.2 years) were evaluated with sonography. Leprosy diagnosis was established on the basis of clinical, bacteriologic, and histopathologic criteria. The reference standard for ulnar neuropathy in this study was clinical symptoms in patients with proven leprosy. The sonographic cross-sectional areas (CSAs) of the ulnar nerve in 3 different regions were obtained. Statistical analyses included Student t tests and receiver operating characteristic curve analysis. The CSAs of the ulnar nerve were significantly larger in the leprosy group than the control group for all regions (P < .01). Sonographic abnormalities in leprosy nerves included focal thickening (90.5%), hypoechoic areas (81%), loss of the fascicular pattern (33.3%), and focal hyperechoic areas (4.7%). Receiver operating characteristic curve analysis showed that a maximum CSA cutoff value of 9.8 mm(2) was the best discriminator (sensitivity, 0.91; specificity, 0.90). Three patients with normal electrophysiologic findings had abnormal sonographic findings. Two patients had normal sonographic findings, of which 1 had abnormal electrophysiologic findings, and the other refused electrophysiologic testing. Sonography and electrophysiology were complementary for identifying ulnar nerve neuropathy in patients with leprosy, with clinical symptoms as the reference standard. This reinforces the role of sonography in the investigation of leprosy ulnar neuropathy.

Reversible Electrocochleographic Abnormalities in Superior Canal Dehiscence

Electrocochleography (ECoG) is often used in the evaluation of episodic vertigo, and abnormal findings are commonly thought to be due to endolymphatic hydrops. We have observed that a number of patients with abnormal ECoG were ultimately found to have superior semicircular canal dehiscence (SSCD). Therefore, we examined the electrocochleographic findings in a series of patients with documented SSCD. Retrospective case series. Academic medical center. Seven adult patients with unilateral SSCD and 4 patients with bilateral SSCD who underwent tympanic ECoG as part of a diagnostic or preoperative evaluation that also included vestibular-evoked myogenic potentials (VEMPs). Patients underwent audiometric testing, ECoG, VEMP, and high-resolution temporal bone computed tomography reformatted to optimally view the superior semicircular canal. Five patients underwent superior canal obliteration. Postoperative VEMP and ECoG were performed in 4 of these patients. Intraoperative continuous ECoG was performed in 1 patient. Summating potential to action potential (SP/AP) ratio on ECoG. Fourteen of 15 ears confirmed to have SSCD on computed tomographic imaging were found to have an elevated SP/AP ratio (defined as >0.40). In one patient with bilateral SSCD, the ear with the radiographically less severe dehiscence had an SP/AP ratio of 0.40, at the upper limit of normal, and a normal VEMP threshold. In all 4 patients who underwent obliteration of the dehiscent canal, and for whom postoperative test results were available, the SP/AP ratio normalized in the operated ear. In the 1 patient who underwent intraoperative ECoG, the SP/AP ratio normalized immediately after canal occlusion. An elevated SP/AP ratio seems to be a consistent finding in SSCD syndrome and, like the other abnormal audiometric and electrophysiologic findings associated with the syndrome, normalizes after surgical correction. Elevation of the SP/AP ratio has historically been associated with endolymphatic hydrops. The present findings expand the differential diagnosis of an abnormal ECoG and may shed light on the origin of an elevated summating potential.