Median somatosensory evoked potential intraoperative monitoring: recommendations based on signal-to-noise ratio analysis.

OBJECTIVE: To form median somatosensory evoked potential (SEP) monitoring recommendations based on signal-to-noise ratio (SNR). METHODS: Two 1024-sweep right median SEP trials were recorded in 35 patients undergoing spine surgery. The SNR (signal power/noise power) and sweeps to reproducibility (<30% and <20% signal variation) were compared between the following derivations: cubital fossa (CF), Erb's point (EPi-EPc, EPi-M, EPi-Fz), cervical (C5S-EPc, C5S-AC, C5S-M, C5S-Fz), subcortical (CPi-EPc, CPi-M), and cortical (CPc-EPc, CPc-M, CPc-FPz, CPc-Fz, CPc-CPi, CPc-CPz), where M was the mastoid. RESULTS: Higher SNR produced markedly faster reproducibility. The CF derivation had very high SNR and single-sweep reproducibility. Of cortical derivations, CPc-CPz had highest mean SNR and fastest overall reproducibility (median 50 and 120 sweeps to <30% and <20% signal variation); occasionally CPc-Fz or CPc-CPi was better. Of Erb's point and cervical derivations, EPi-M and C5S-M had highest mean SNR and fastest reproducibility. Subcortical derivations had very low mean SNR and slow or non-reproducibility. High voltage EEG degraded cortical and subcortical derivation SNR and reproducibility in young children. CONCLUSIONS: The highest SNR derivations should be used to speed surgical feedback; slower low-SNR derivations should be omitted. Consequently, the CF is the best technical control and CPc-CPz should be the standard cortical derivation, with CPc-Fz and CPc-CPi as alternates. EPi-M and C5S-M are the best Erb's point and cervical derivations, but are optional. Subcortical derivations should be omitted. A presence/absence criterion or SEP omission may be indicated for some young children. SIGNIFICANCE: The results should influence future guidelines.

Tibial somatosensory evoked potential intraoperative monitoring: recommendations based on signal to noise ratio analysis of popliteal fossa, optimized P37, standard P37, and P31 potentials.

OBJECTIVE: To compare the intraoperative signal-to-noise ratio (SNR), reproducibility and rapidity of popliteal fossa (PF), optimized P37, standard P37 and P31 potentials. METHODS: Raw sweeps and 11 averages doubling sweep number from 2 to 2048 were compared in 37 patients undergoing scoliosis surgery. Optimized (highest amplitude or SNR) P37 derivations were Cz-CPc (22), CPz-CPc (27), Pz-CPc (7), iCPi-CPc (8), CPi-CPc (1), Cz-Pz (2) or Pz-FPz (3), and in two patients with non-decussation, Cz-CPi (1) or CPz-CPi (3). Standard P37 and P31 derivations were CPz-FPz and FPz-C5S. Signal amplitude was measured in 2048-sweep averages; peak noise was measured in raw sweeps and +/- averages; SNR was amplitude/noise. Visual superimposability and < 20-30% amplitude variation determined reproducibility. Sweeps to reproducibility determined rapidity. RESULTS: The SNR order was PF >> optimized P37 > standard P37 > P31. Mean optimized P37 SNR advantages over the standard P37 and P31 were 2.1:1 and 4.9:1. SNR had powerful non-linear correlations to reproducibility and rapidity. Median sweeps to reproducibility were PF: 2, optimized P37: 128, standard P37: 512 and P31: 1024. EEG noise was greatest in FPz derivations. Burst-suppression increased scalp potential SNR and rapidity. CONCLUSIONS: Optimized P37 and PF recordings are most rapidly reproducible due to superior SNRs and are recommended. FPz should be avoided. Burst-suppression may be desirable. SIGNIFICANCE: CPz-FPz and FPz-C5S should no longer be standard.

Neurologic features of horizontal gaze palsy and progressive scoliosis with mutations in ROBO3.

OBJECTIVE: To review the neurologic, neuroradiologic, and electrophysiologic features of autosomal recessive horizontal gaze palsy and progressive scoliosis (HGPPS), a syndrome caused by mutation of the ROBO3 gene on chromosome 11 and associated with defective decussation of certain brainstem neuronal systems. METHODS: The authors examined 11 individuals with HGPPS from five genotyped families with HGPPS. Eight individuals had brain MRI, and six had electrophysiologic studies. RESULTS: Horizontal gaze palsy was fully penetrant, present at birth, and total or almost total in all affected individuals. Convergence, ocular alignment, congenital nystagmus, and vertical smooth pursuit defects were variable between individuals. All patients developed progressive scoliosis during early childhood. All appropriately studied patients had hypoplasia of the pons and cerebellar peduncles with both anterior and posterior midline clefts of the pons and medulla and electrophysiologic evidence of ipsilateral corticospinal and dorsal column-medial lemniscus tract innervation. Heterozygotes were unaffected. CONCLUSIONS: The major clinical characteristics of horizontal gaze palsy and progressive scoliosis were congenital horizontal gaze palsy and progressive scoliosis with some variability in both ocular motility and degree of scoliosis. The syndrome also includes a distinctive brainstem malformation and defective crossing of some brainstem neuronal pathways.

A comparison between derivation optimization and Cz'-FPz for posterior tibial P37 somatosensory evoked potential intraoperative monitoring.

OBJECTIVE: To compare P37 derivation optimization to Cz'-FPz. METHODS: After induction in 120 patients, monitoring derivations optimized by mapping FPz, Cz, Cz', Pz, C4', C2', C1' and C3'-mastoid to determine the P37 and N37 maximums for use as inputs 1 and 2 were compared to Cz'-FPz. This was repeated later in 35 surgeries. RESULTS: Eleven optimal derivations occurred and usually differed between sides. Input 1 was Cz', Pz, Cz, iCi', or Ci' and input 2 was Cc', FPz, Ci' or Pz. Even the most frequent Cz'-Cc' derivation was optimal for both sides of an individual in only 17% and this was true for Cz'-FPz in only 4%. Optimization produced higher amplitudes than Cz'-FPz (P<0.001). The ratio was [squareroot of 2] : 1 in 61% of patients and > or =2:1 in 28%, approximately halving or quartering averaging times. Optimization assessed decussation, disclosing non-decussation in one patient while Cz'-FPz did not. Alterations of P37 topography that reduced initially optimal derivation amplitude and made a different derivation optimal were demonstrated by repeat optimization in 13 of 35 patients, preventing misinterpretation in one. While also affected, Cz'-FPz neither detected nor adjusted for potentially misleading topographic changes. CONCLUSIONS: Higher amplitudes, decussation assessment and topographic adjustment make P37 derivation optimization superior to Cz'-FPz for monitoring this highly variable potential.

Intraoperative neurophysiologic discovery of uncrossed sensory and motor pathways in a patient with horizontal gaze palsy and scoliosis.

OBJECTIVE: To report the intraoperative neurophysiologic discovery of clinically unsuspected non-decussation of the somatosensory and motor pathways. METHODS: We performed somatosensory evoked potential (SEP) and transcranial electric stimulation (TES) muscle motor evoked potential (MEP) monitoring during scoliosis surgery for a 16 year old patient with familial horizontal gaze palsy and progressive scoliosis. Our routine procedures included optimizing tibial cortical SEP monitoring derivations through saggital and coronal (C4', C2', Cz', C1', C3'-mastoid) P37 mapping, which surprisingly indicated non-decussation. Consequently, we also obtained coronal median nerve SEPs and simultaneous bilateral muscle recordings to lateralized TES (C3-Cz, C4-Cz) intraoperatively and focal hand area transcranial magnetic stimulation (TMS) postoperatively. RESULTS: For each nerve, tibial P37/N37 distribution was contralateral/ipsilateral and median N20 ipsilateral. For each hemisphere, ipsilateral TES MEPs had lower thresholds and TMS MEPs were exclusively ipsilateral. Accurate monitoring required reversed montages. Reevaluation of an MRI (previously reported normal) disclosed a ventral midline cleft of the medulla. CONCLUSIONS: The results indicate uncrossed dorsal column-medial lemniscal and corticospinal pathways due to brain-stem malformation with absent internal arcuate and pyramidal decussations. SIGNIFICANCE: Simultaneous bilateral recording to unilateral stimulation demonstrates SEP/MEP hemispheric origin and is important for accurate interpretation and monitoring because decussation anomalies exist.

Transcranial magnetic stimulation in Behçet's disease: a cross-sectional and longitudinal study with 44 patients comparing clinical, neuroradiological, somatosensory and brain-stem auditory evoked potential findings.

OBJECTIVES: To compare neurological involvement in Behçet's disease as documented by transcranial magnetic stimulation (TMS) with clinical, neuroradiological, somatosensory (SEP) and auditory evoked potential (BAEP) findings. METHODS: Forty-four patients were studied over an 8 year period. Nine patients had follow-up studies done. TMS central motor conduction (CMC) studies to upper and lower limb muscles, brain magnetic resonance imaging (MRI), SEP, and BAEP testing were conducted. RESULTS: Thirty-nine patients had CMC slowing, decreased amplitude or absent motor evoked potentials (MEP); 5 of these patients were neurologically normal. Concordance of TMS results, clinical deficits, and MRI findings occurred in 36 of the 39 patients. SEP and BAEP testing proved non-complementary to MEP. Generally, follow-up studies revealed faster CMC and higher MEP amplitude. However, in two patients the CMC time to one target muscle became prolonged with diminished MEP amplitude over a period of 1.5-3 years. CONCLUSIONS: TMS can be useful in detecting and quantifying motor tract dysfunction in Behçet's disease and provides functional information complementary to imaging studies. TMS is more sensitive than either SEP or BAEP. Our longitudinal studies suggest that TMS studies may be valuable in monitoring disease activity or therapeutic response.

Risk factors in wound infections after laparotomy in obstetrics and gynaecology.

BACKGROUND: The objectives of the study are to obtain risk factors for and rates in postoperative wound infections in order to develop an infection surveillance program. METHODS: A retrospective, case-controlled three-year study of wound infections in Caesarean sections and gynaecological laparotomies with 15 predictive variables. For each patient and variable, the likelihood ratio of having infection was calculated. The prior odds of infection were iteratively combined by a set of predictive variables to establish the posterior probability of being infected. A patient was classified as pathological if the posterior probability was above 0.5 and as normal if the posterior probability was below 0.5. The squared risk of misclassification was used as indicator of the goodness of classification. RESULTS: Ruptured membranes prior to Caesarean section classified 88% of the patients correctly. For gynaecological laparotomies body mass index classified 76% of the patients correctly. The remaining predictive variables added little to improve the classification. CONCLUSIONS: Infection surveillance programs may reduce wound infection rates and have been recommended because they offer increased service quality, safer guidance for the implemantation of preventive measures, and better patient information. We have demonstrated that the number of predictive variables necessary in registering Caesarean sections can be limited to one or two, and in gynaecological laparotomies to one to three.

Lower urinary tract symptoms--a population survey using the Danish Prostatic Symptom Score (DAN-PSS) questionnaire.

OBJECTIVE: To describe voiding problems and the trouble they cause in a Danish population. Furthermore, to find symptoms specific for the ageing man, and thereby symptoms that might relate to an enlarged prostate. MATERIAL AND METHODS: The DAN-PSS questionnaire was mailed to a gender- and age-stratified random sample of 500 inhabitants in Herlev municipality. Prevalence of the symptoms and the trouble they cause were calculated and related to age and gender by the x2 test for trend and the chi2 test, respectively. RESULTS: The response rate was 73.6%. In total, 84.5% of the subjects had experienced at least one symptom within the previous fortnight. The various symptom prevalences ranged from 3.8-67.1%. Although many subjects experienced symptoms, they were not always bothered by them, and women were generally more bothered than men. Weak stream, hesitancy and dribbling occurred more often among men, whereas incontinence (stress, mixed) occurred more often among women. Nocturia and mixed incontinence increased in prevalence with increasing age among both men and women. Weak stream, incomplete emptying, stress and urge incontinence showed an age-related increase in prevalence among men, but not among women. These might therefore be symptoms of an enlarged prostate. CONCLUSION: Lower urinary tract symptoms occur with high prevalence in the background population, but they do not always cause trouble. Weak stream, incomplete emptying, stress and urge incontinence seem to be symptoms of an enlarged prostate.

Miyoshi myopathy in Saudi Arabia: clinical, electrophysiological, histopathological and radiological features.

Miyoshi myopathy (MM) is a rare autosomal recessive distal myopathy linked to chromosome 2p12-14 that has not been described in Saudi Arabia. A Saudi family with five siblings aged 3-25 years, an unrelated 18-year-old woman and a 40-year-old man with MM were identified. All patients underwent a neurological examination, serum chemistry, electromyography and MRI of the legs. Four patients underwent a muscle biopsy that was processed for routine enzyme histochemistry and immunocytochemical analyses for dystrophin and adhalin (alpha-sarcoglycan). The two sporadic and two familial cases showed classic findings of MM, including early adult onset, preferential involvement of gastrocnemius muscles, markedly elevated serum creatine kinase levels and dystrophic-appearing muscle without vacuoles. Magnetic resonance imaging revealed selective involvement of the posterior compartment muscles and myoedema by STIR sequences. The remaining three familial cases had elevated serum creatine kinase levels and two also had early myopathic findings by EMG suggestive of MM.

Serial MRI, VEP, SEP and biotesiometry in acute optic neuritis: value of baseline results to predict the development of new lesions at one year follow up.

INTRODUCTION: In an attempt to establish the value of MRI, VEP, SEP, and biotesiometry in monitoring disease evolution we undertook a one year follow up study of 70 untreated patients with acute optic neuritis (ON). MATERIAL & METHODS: ON was monosymptomatic in 48 patients (bilateral in 10) and part of clinically definite multiple sclerosis (CDMS) in 22 patients, examined as mentioned below. RESULTS: Results are given at onset and at follow up (in brackets). In monosymptomatic ON, brain MRI was abnormal in 53% (53%), VEP in the eye with acute ON in 79% (71%), VEP in the clinically unaffected eye in 34% (47%), SEP in 25% (23%), and biotesiometry in 29% (17%). In CDMS, brain MRI was abnormal in 95% (95%), VEP in the eye with acute ON in 86% (77%), VEP in the clinically unaffected eye in 50% (64%), SEP in 55% (50%), and biotesiometry in 63% (53%). Only minor changes in test scores were observed after one year except for significant improvement of VEP in eyes with acute ON. Eight of 32 patients, characterized by at least one abnormal paraclinical test at onset of monosymptomatic ON, had developed CDMS versus none of 16 patients with normal paraclinical results (p = 0.03; Fisher). CONCLUSION: Patients with monosymptomatic ON with paraclinical signs of multifocal involvement at onset had an increased risk of developing CDMS. No single test predicted the evolution of CDMS, perhaps due to the relatively short follow up time.

Familial childhood primary lateral sclerosis with associated gaze paresis.

Three children from consanguineous parents began losing the ability to walk in late infancy. Despite chronically progressive weakness leading to wheelchair dependence by adolescence and later loss of motor speech production, intellect remained preserved. Examination revealed upper motor neuron findings of pseudobulbar palsy and spastic quadriplegia, without dementia, cerebellar, extrapyramidal or sensory signs. In addition they exhibited a diffuse conjugate saccadic gaze paresis, especially severe on down-gaze. CT and MRI scans of brain and spinal cord, EEGs, visual and brainstem auditory evoked potentials, CSF examinations, enzyme assays for lysosomal storage diseases, blood amino acids and urine organic acids were all normal. Cortical somatosensory evoked potentials were poorly configured in two of the patients, though they had normal central conduction. EMG showed no signs of denervation. Nerve conduction studies showed normal peripheral motor and sensory conduction velocities. Transcranial magnetic stimulation of the brain elicited no motor-evoked potentials. Despite the lack of neuropathological confirmation, the clinical course and neurophysiologic data strongly support the diagnosis of a familial (autosomal recessive) primary lateral sclerosis (PLS).

Sleep apnea syndrome: A report of 20 Saudi patients.

Patients with sleep apnea syndrome (SAS) suffer considerable morbidity and increased mortality. The most common symptoms of SAS include excessive daytime sleepiness, nocturnal breath cessation, snoring and gasping sounds. We reviewed the characteristics of 20 Saudi patients with sleep apnea (15 males, five females) who were studied at our tertiary care center in 1992 and 1993. The ages ranged from 15 to 61 years. All were obese. Two each were acromegalic and hypothyroid. Hypertension was noted in seven (35%) patients and one had symptomatic bradycardia. Two (10%) patients presented with recurrent pulmonary emboli and two were involved in multiple road traffic accidents as a result of falling asleep while driving. One male student had poor performance at school. Three patients were known to have chronic obstructive airway disease. Six males and one female were hypercapnic (PCO2; > 6.1 kPa) while 10 patients had hypoxemia (paO2; < 8.0 kPa). Four patients were polycythemic. Pulmonary function tests showed that 15 (75%) had restrictive patterns, three (15%) had obstructive patterns and two (10%) had mixed patterns. A "saw-tooth" pattern was seen in the inspiratory limb of a flow-volume curve in four patients. Daytime polysomnography showed that eight had obstructive sleep apnea, four had central sleep apnea and six had mixed type sleep apnea. Both hypothyroid patients improved with replacement therapy; one acromegalic patient and one patient with tracheal stenosis responded to specific treatment. Nasal positive airway pressure machine (BIPAPtrade mark Resperonics Inc) was effective in relieving apnea and reducing symptoms in five patients. None of the patients were able to lose a substantial amount of weight. All these patients were investigated extensively at different places prior to establishing the diagnosis.

Familial tremulous and myoclonic dystonia with white matter changes in brain magnetic resonance imaging.

We report two families with a disorder, probably autosomal recessive, characterized by tremor of juvenile onset, dystonia, and myoclonus with preserved cognitive, cerebellar, and peripheral nervous system functions. During 4 years' follow-up, mild spasticity appeared. Magnetic resonance imaging (MRI) revealed mild diffuse changes in the white matter. Central conduction times for visual, motor, and sensory systems were all prolonged. Extensive metabolic work-up failed to reveal lysosomal, peroxisomal, mitochondrial, or other metabolic abnormalities.

Neurophysiologic correlates of organic acidemias: a survey of 107 patients.

The files of 107 patients with 19 different types of organic acidemia were reviewed retrospectively. Approximately 50% of the patients had abnormal electroencephalogram (EEG) at the time of initial study. In patients who had serial studies, the EEG deteriorated in 38% and improved in 15%. The predominant EEG abnormality encountered was slowing of the background activity in various degrees. Focal or generalized paroxysmal activity occurring in conjunction with slow background activity indicated a poor prognosis. Brainstem auditory evoked potentials (BAEP), visual evoked potentials (VEP), and somatosensory evoked potentials (SEP) were analyzed. The VEP was abnormal in 44%, BAEP in 39%, and SEP in 29% of the patients. Given the magnitude and frequency by which neurophysiological abnormalities occur in organic acidemias, neurophysiology testing provides complementary functional information and has an important place in the clinical work-up of these diseases.

Evoked potential findings in Behçet's disease. Brain-stem auditory, visual, and somatosensory evoked potentials in 44 patients.

We studied 54 patients with Behçet's disease, 41 males and 13 females, mean age 28 years. Forty-four patients had auditory brain-stem evoked potential (BAEP) recordings, 39 had pattern reversal visual evoked potentials (VEP), 27 had median nerve somatosensory evoked potential (SEP) recordings, and 25 tibial nerve SEPs. BAEPs were abnormal in 16 patients (52%) with neurological manifestations and in 4 (31%) without, because of decreased amplitude of wave V, prolonged I-III or III-V interpeak latencies, or uncertain/absent waves III and/or V. Eleven patients (40%) with neurological symptoms and 3 patients (25%) without, had abnormal VEPs. Absent potentials, decreased amplitude, with or without prolonged P100 latency, were found in 75% of the cases, the rest had prolonged P100 latency only. Median SEPs were abnormal in 8 patients (38%) with neurological manifestations. Four patients (21%) had abnormal tibial SEPs. Decreased amplitude with or without mild slowing in central conduction was the predominant SEP abnormality. SEPs were normal in all patients without neurological symptoms. In total, 84% of patients with, and 38% of patients without, neurological symptoms had abnormalities of one or more EP modality. When used cautiously, EP studies in Behçet's disease might be helpful to separate neuro-Behçet from other disorders with similar symptomatology, to disclose subclinical CNS involvement, to evaluate and monitor CNS disease activity, and to provide objective measures of treatment response.

Precision of a patient-weighted symptom score in prostatism. The DAN-PSS-1 questionnaire.

The Danish Prostatic Symptom Score (DAN-PSS-1) comprises 12 questions related to voiding problems in benign prostatic hyperplasia. The patient himself scores each symptom as regards severity (symptom score) and impact on daily life (bother score). The precision of this patient-weighted (postal) questionnaire was investigated in terms of repeat frequencies of replies from 197 randomly selected men on two sequential occasions. The questionnaire was well understood by the patients. The median frequency of repeat in answers to the questions was 83.5% (range 0-99.7%). This frequency depended on the nature of the question and the severity or bother of the symptom. Repeatability as regards bother rose markedly when the bother score was made dependent of the symptom score, suggesting a relationship between the two. As with other questionnaires, the precision of those dealing with prostatism should be established before clinical use. The observed relationship between symptom score and bother score may be of diagnostic value.

Combined oral isoprinosine-intraventricular alpha-interferon therapy for subacute sclerosing panencephalitis.

Eighteen patients, 16 boys and 2 girls, aged 5-14 years, with subacute sclerosing panencephalitis (SSPE) were treated with oral isoprinosine (100 mg/kg/day) and intraventricular alpha-interferon 2b (Intron A, Schering Corp.), starting at 500,000 U twice a week and later increasing to 3 million U biweekly. Minimal follow-up of living patients is 12 months; maximal 40 months. On the basis of the Neurological Disability Index (NDI) scores and staging, 8 have treatment-induced remissions (3 improved, 5 arrested), 4 are worse and 6 died. This 44% (8/18) rate of remission/improvement compares well with the 9% (1/11) remission in historical controls in the same institution (p = < 0.05) and 5% spontaneous remission in the literature. Combined oral isoprinosine-intraventricular alpha-interferon appears to be an effective treatment for SSPE.