Strain level microbial detection and quantification with applications to single cell metagenomics.

Computational identification and quantification of distinct microbes from high throughput sequencing data is crucial for our understanding of human health. Existing methods either use accurate but computationally expensive alignment-based approaches or less accurate but computationally fast alignment-free approaches, which often fail to correctly assign reads to genomes. Here we introduce CAMMiQ, a combinatorial optimization framework to identify and quantify distinct genomes (specified by a database) in a metagenomic dataset. As a key methodological innovation, CAMMiQ uses substrings of variable length and those that appear in two genomes in the database, as opposed to the commonly used fixed-length, unique substrings. These substrings allow to accurately decouple mixtures of highly similar genomes resulting in higher accuracy than the leading alternatives, without requiring additional computational resources, as demonstrated on commonly used benchmarking datasets. Importantly, we show that CAMMiQ can distinguish closely related bacterial strains in simulated metagenomic and real single-cell metatranscriptomic data.

Vertical cavity capacitive transducer.

The capacitive micromachined ultrasonic transducer (CMUT) has inherent advantages, such as larger bandwidth and monolithic integration capability with electronics, when compared to the piezoelectric transducer. The most significant shortcoming of the device is the trade-off between input and output sensitivities. Adequate receive sensitivity requires an electric field intensity on the order of 105 V/m, which can be achieved by sub-micron gap heights. However, a small gap limits the device stroke and, consequently, the maximum output pressure. This paper addresses this problem by proposing a CMUT with a vertical cavity. The membrane of the device has a piston part that is surrounded by the sidewalls of a vertical cylinder formed in the substrate. The fringing electric field pulls the piston in the vertical direction; hence, the gap height remains fixed, which alleviates the hard limit on device stroke. The performance of the proposed device is compared to that of the conventional CMUT by theoretical and analytical methods, and a micro-fabrication method is devised. Additionally, a millimeter-scale device has been manufactured and tested as a proof of concept.

Concordance of sexual dysfunction and dissatisfaction by self-report and those by partner's perception in young adult couples.

We evaluated concordance levels of young adult spouses (N=107 couples, total N=214) with regards to sexual satisfaction by using Golombock-Rust Inventory of Sexual Satisfaction (GRISS). Each spouse of the couples filled out both female and male forms of the GRISS. Self- and spouse-reported scores were analyzed in terms of inter-rater correlation and agreement. The prevalence of overall sexual dissatisfaction was 10.3% and 26.2% in wives and husbands, respectively. The correlation coefficient (r) between the self-reported overall sexual satisfaction scores and those assessed by the spouses was 0.25 (P=0.014) and 0.04 (P=0.680) for wives and husbands, respectively. The sensitivity for perception of partner's sexual problems ranged 11% to 47%, and the specificity was around 64% to 100%, except for vaginismus, which had a sensitivity of 83% and a specificity of 25%. The prevalance-adjusted and bias-adjusted kappa (PABAK) value for overall sexual dissatisfaction reported by themselves and that assessed by their spouses was 0.68 and 0.16 for the wives and husbands, respectively. For specific female sexual problems, the PABAK value was the highest in female dissatisfaction (0.81) followed by anorgasmia (0.78), female avoidance (0.44), vaginismus (0.44), infrequency (0.33), non-communication (0.14) and female nonsensuality (0.14). For specific male sexual problems, the PABAK value was the highest in male nonsensuality (1.00), followed by male dissatisfaction (0.78), infrequency (0.46), non-communication (0.42), male avoidance (0.36), impotence (0.27) and premature ejaculation (-0.04). Our findings suggested that in this clinical sample the partner's perception of sexual dysfunction and dissatisfaction did not correlate well with the subject's self-reported sexual problems, and generally male sexual problems were less correctly perceived by the partners than were female sexual problems. This result may provide helpful information for clinicians who take care of patients' sexual problems.

Levels of neopterin and C-reactive protein in pregnant women with fetal growth restriction.

The aim of this study was to evaluate whether pregnant women with fetal growth restriction (FGR) have higher plasma neopterin and C-reactive protein (CRP) concentrations compared with those with uncomplicated pregnancy. A total of 34 pregnant women with FGR and 62 patients with uncomplicated pregnancy were included. Neopterin and CRP levels were measured at the time of diagnosis. The primary outcome of this study was to compare the neopterin and CRP levels in pregnant women with FGR and those with uncomplicated pregnancies. The secondary outcome of our study was to evaluate the correlation between fetal birth weight and maternal neopterin levels. The serum neopterin levels were significantly elevated in pregnant women with FGR (22.71 ± 7.70 vs 19.15 ± 8.32). However, CRP was not elevated in pregnant women with FGR (7.47 ± 7.59 vs 5.29 ± 3.58). These findings support the hypothesis that pregnancy with FGR is associated with a marked increase in macrophage activation and the natural immune system.

Changes in the ovarian stromal blood flow in patients treated with laparoscopic salpingostomy for ectopic pregnancy.

This study is aimed to evaluate the impact of laparoscopic salpingostomy on ovarian stromal blood flow indices in patients with ectopic pregnancy, and to compare the ovarian stromal blood flow indices with matched paired healthy women. We included 37 patients who underwent laparoscopic salpingostomy and 37 age- and parity-matched women as controls. The main outcome was the differences in ovarian volume, antral follicle count (AFC), and ovarian stromal blood flow indices between the study group participants after the surgery and the healthy controls. Comparison of the ovarian parameters between the study group after the surgery and the control group revealed no significant differences in terms of ovarian volume (p = 0.783), AFC (p = 0.253), ovarian stromal S/D ratios (p = 0.054), pulsatility index (PI; p = 0.938) and resistance index (RI; p = 0.041). In addition, comparison of the ovarian parameters before and after the surgical treatment revealed no significant differences in the ovarian volume (p = 0.141), AFC (p = 0.084), ovarian stromal S/D ratios (p = 0.187), PI (p = 0.102) and RI (p = 0.108). In conclusion, laparoscopic salpingostomy does not affect ovarian function in terms of ovarian stromal blood flow indices, ovarian volume, and AFC.

Hopelessness and social comparison in Turkish adolescent with visual impairment.

The purpose of this study was to determine visually impaired adolescents' level of hopelessness and how they perceive of themselves socially compared to other individuals. Another purpose of this study was to look for relationships between hopelessness and social comparison in adolescents with visual impairment. The research population was comprised of 130 students at a secondary school for the visually impaired in Istanbul, Turkey. Our study demonstrated a weak relationship between social comparison and hopelessness (r=-0.46, P < 0.000). The mean hopelessness score for the adolescents with visual impairment was 4.59 ± 3.12 (girls: 4.23 ± 3.10; boys: 4.83 ± 3.11) and social comparison score was 87.50 ± 11.19 (girls: 88.67 ± 11.62; boys: 86.60 ± 10.85). Hopelessness and social comparison were not affected by being blind from birth compared to later or from being a full-time boarding student compared to being a day student. The hopeless (Beck Hopelessness Scale score ≥ 9) adolescents' social comparison scores were found lower than hopeful ones' scores (P < 000). Factors affecting hopelessness and social comparison were feelings about their father, teacher and school.

Analytical and numerical calculations of optimum design frequency for focused ultrasound therapy and acoustic radiation force.

Focused ultrasound therapy relies on acoustic power absorption by tissue. The stronger the absorption the higher the temperature increase is. However, strong acoustic absorption also means faster attenuation and limited penetration depth. Hence, there is a trade-off between heat generation efficacy and penetration depth. In this paper, we formulated the acoustic power absorption as a function of frequency and attenuation coefficient, and defined two figures of merit to measure the power absorption: spatial peak of the acoustic power absorption density, and the acoustic power absorbed within the focal area. Then, we derived "rule of thumb" expressions for the optimum frequencies that maximized these figures of merit given the target depth and homogeneous tissue type. We also formulated a method to calculate the optimum frequency for inhomogeneous tissue given the tissue composition for situations where the tissue structure can be assumed to be made of parallel layers of homogeneous tissue. We checked the validity of the rules using linear acoustic field simulations. For a one-dimensional array of 4cm acoustic aperture, and for a two-dimensional array of 4×4cm(2) acoustic aperture, we found that the power absorbed within the focal area is maximized at 0.86MHz, and 0.79MHz, respectively, when the target depth is 4cm in muscle tissue. The rules on the other hand predicted the optimum frequencies for acoustic power absorption as 0.9MHz and 0.86MHz, respectively for the 1D and 2D array case, which are within 6% and 9% of the field simulation results. Because radiation force generated by an acoustic wave in a lossy propagation medium is approximately proportional to the acoustic power absorption, these rules can be used to maximize acoustic radiation force generated in tissue as well.

Capacitive micromachined ultrasonic transducers with piston-shaped membranes: fabrication and experimental characterization.

Capacitive micromachined ultrasonic transducers (CMUTs) featuring piston-shaped membranes (piston CMUTs) were developed to improve device performance in terms of transmission efficiency, reception sensitivity, and fractional bandwidth (FBW). A piston CMUT has a relatively flat active moving surface whose membrane motion is closer to ideal piston-type motion compared with a CMUT with uniformly thick membranes (classical CMUT). Piston CMUTs with a more uniform surface displacement profile can achieve high output pressure with a relatively small electrode separation. The improved device capacitance and gap uniformity also enhance detection sensitivity. By adding a center mass to the membrane, a large ratio of second-order resonant frequency to first-order resonant frequency was achieved. This improved the FBW. Piston CMUTs featuring membranes of different geometric shapes were designed and fabricated using wafer bonding. Fabricating piston CMUTs is a more complex process than fabricating CMUTs with uniformly thick membranes. However, no yield loss was observed. These devices achieved ~100% improvement in transduction performance (transmission and reception) over classical CMUTs. For CMUTs with square and rectangular membranes, the FBW increased from ~110% to ~150% and from ~140% to ~175%, respectively, compared with classical CMUTs. The new devices produced a maximum output pressure exceeding 1 MPa at the transducer surface. Performance optimization using geometric membrane shape configurations was the same in both piston CMUTs and classical CMUTs.

Oral diadochokinesis and velocity of narrative speech: a prognostic parameter for the outcome of diffuse axonal injury in severe head trauma.

AIM: To investigate dysarthria in severe traumatic brain injury following an acceleration/deceleration trauma and to correlate results with the severity of head trauma. METHODS: Oral diadochokinesis by testing alternating (/pa/, /ta/and/ka/) and sequential motion rates (/pataka/and/tana/) and contextual speech, which comprises narrative speech and text reading, were examined in 15 patients in the chronic stage after severe closed head trauma with diffuse axonal injury. A possible influence of the severity of brain injury, expressed by the duration of post-traumatic amnesia, was examined. RESULTS: Oral diadochokinesis of alternating motion rates and velocity of narrative speech were significantly reduced in traumatic brain injury. Both parameters correlated highly significantly with each other and correlated with the severity of brain injury described by the duration of post-traumatic amnesia. Reading speed was not comparable with narrative speech. Reading speed did not correlate with diffuse axonal injury but was strongly influenced by parameters that also influenced mental abilities. CONCLUSION: Oral diadochokinetic abilities of alternating motion rates and velocity of narrative speech represent a possible additional prognostic parameter for the outcome of traumatic brain injury in diffuse axonal injury.

Integration of 2D CMUT arrays with front-end electronics for volumetric ultrasound imaging.

For three-dimensional (3D) ultrasound imaging, connecting elements of a two-dimensional (2D) transducer array to the imaging system's front-end electronics is a challenge because of the large number of array elements and the small element size. To compactly connect the transducer array with electronics, we flip-chip bond a 2D 16 x 16-element capacitive micromachined ultrasonic transducer (CMUT) array to a custom-designed integrated circuit (IC). Through-wafer interconnects are used to connect the CMUT elements on the top side of the array with flip-chip bond pads on the back side. The IC provides a 25-V pulser and a transimpedance preamplifier to each element of the array. For each of three characterized devices, the element yield is excellent (99 to 100% of the elements are functional). Center frequencies range from 2.6 MHz to 5.1 MHz. For pulse echo operation, the average - 6-dB fractional bandwidth is as high as 125%. Transmit pressures normalized to the face of the transducer are as high as 339 kPa and input-referred receiver noise is typically 1.2 to 2.1 mPa/pHz. The flip-chip bonded devices were used to acquire 3D synthetic aperture images of a wire-target phantom. Combining the transducer array and IC, as shown in this paper, allows for better utilization of large arrays, improves receive sensitivity, and may lead to new imaging techniques that depend on transducer arrays that are closely coupled to IC electronics.

Predicting lactate threshold using ventilatory threshold.

Lactate threshold is an important reference point when setting training intensities for endurance athletes. Ventilatory threshold has been used as a noninvasive estimate of lactate threshold, but appears to underestimate training intensity for many athletes. This study evaluated whether data obtained during a noninvasive, maximal exercise test could be used to predict lactate threshold. Maximal oxygen consumption (55+/-2 ml O(2) x kg(-1) x min(-1)) and heart rate at the ventilatory threshold (V-slope method) were determined for 19 cyclists (10 men, 9 women, 35+/-2 years). Cyclists also performed a lactate threshold test, consisting of 8 min stages at power outputs below, at, and above the ventilatory threshold. Heart rate associated with the lactate threshold was determined using the Dmax method. The correlation coefficient between heart rates at the ventilatory and lactate thresholds was 0.67, indicating 45% shared variance. The best fitting model to predict heart rate at the lactate threshold included heart rate at the ventilatory threshold, gender, body weight, and an interaction between gender and body weight. Using this model, R(2) was 0.70. Thus, heart rate at the ventilatory threshold may be adjusted to more accurately predict a heart rate that corresponds to the lactate threshold for recreational cyclists.

Capacitive micromachined ultrasonic transducers (CMUTs) with isolation posts.

In this paper, an improved design of a capacitive micromachined ultrasonic transducer (CMUT) is presented. The design improvement aims to address the reliability issues of a CMUT and to extend the device operation beyond the contact (collapse) voltage. The major design novelty is the isolation posts in the vacuum cavities of the CMUT cells instead of full-coverage insulation layers in conventional CMUTs. This eliminates the contact voltage drifting due to charging caused by the insulation layer, and enables repeatable CMUT operation in the post-contact regime. Ultrasonic tests of the CMUTs with isolation posts (PostCMUTs) in air (electrical input impedance and capacitance vs. bias voltage) and immersion (transmission and reception) indicate acoustic performance similar to that obtained from conventional CMUTs while no undesired side effects of this new design is observed.

Forward-looking intracardiac ultrasound imaging using a 1-D CMUT array integrated with custom front-end electronics.

Minimally invasive catheter-based electrophysiological (EP) interventions are becoming a standard procedure in diagnosis and treatment of cardiac arrhythmias. As a result of technological advances that enable small feature sizes and a high level of integration, nonfluoroscopic intracardiac echocardiography (ICE) imaging catheters are attracting increasing attention. ICE catheters improve EP procedural guidance while reducing the undesirable use of fluoroscopy, which is currently the common catheter guidance method. Phased-array ICE catheters have been in use for several years now, although only for side-looking imaging. We are developing a forward-looking ICE catheter for improved visualization. In this effort, we fabricate a 24-element, fine-pitch 1-D array of capacitive micromachined ultrasonic transducers (CMUT), with a total footprint of 1.73 mm x 1.27 mm. We also design a custom integrated circuit (IC) composed of 24 identical blocks of transmit/ receive circuitry, measuring 2.1 mm x 2.1 mm. The transmit circuitry is capable of delivering 25-V unipolar pulses, and the receive circuitry includes a transimpedance preamplifier followed by an output buffer. The CMUT array and the custom IC are designed to be mounted at the tip of a 10-Fr catheter for high-frame-rate forward-looking intracardiac imaging. Through-wafer vias incorporated in the CMUT array provide access to individual array elements from the back side of the array. We successfully flip-chip bond a CMUT array to the custom IC with 100% yield. We coat the device with a layer of polydimethylsiloxane (PDMS) to electrically isolate the device for imaging in water and tissue. The pulse-echo in water from a total plane reflector has a center frequency of 9.2 MHz with a 96% fractional bandwidth. Finally, we demonstrate the imaging capability of the integrated device on commercial phantoms and on a beating ex vivo rabbit heart (Langendorff model) using a commercial ultrasound imaging system.

Correlation of seminal parameters with serum lipid profile and sex hormones.

The phospholipids and fatty acid composition of sperm are altered under the influence of serum lipids on impaired seminal parameters in infertile men. We studied the correlation of the serum lipid profile and sex hormone results of a group of infertile men with sperm characteristics of 18 infertile men. Semen samples were collected and analyzed. Serum fasted and post-meal glucose levels, insulin, total cholesterol, HDL, LDL, VLDL, triglyceride, FSH, LH, and testosterone measurements were performed. The increased serum VLDL, total triglyceride, and testosterone values were significantly correlated with decreased sperm motility. Serum FSH values were also inversely correlated with normal sperm morphology. The increased VLDL impaired seminal parameters; additionally, increased triglycerides may have deleterious effects on spermatogenesis. Deterioration is related with increased serum VLDL and triglyceride levels.

Experimental characterization of collapse-mode CMUT operation.

This paper reports on the experimental characterization of collapse-mode operation of capacitive micromachined ultrasonic transducers (CMUTs). CMUTs are conventionally operated by applying a direct current (DC) bias voltage less than the collapse voltage of the membrane, so that the membrane is deflected toward the bottom electrode. In the conventional regime, there is no contact between the membrane and the substrate; the maximum alternating current (AC) displacement occurs at the center of the membrane. In collapse-mode operation, the DC bias voltage is first increased beyond the collapse voltage, then reduced without releasing the collapsed membrane. In collapse-mode operation, the center of the membrane is always in contact with the substrate. In the case of a circular membrane, the maximum AC displacement occurs along the ring formed between the center and the edge of the membrane. The experimental characterization presented in this paper includes impedance measurements in air, pulse-echo experiments in immersion, and one-way optical displacement measurements in immersion for both conventional and collapse-mode operations. A 205-microm x 205-microm 2-D CMUT array element composed of circular silicon nitride membranes is used in the experiments. In pulse-echo experiments, a custom integrated circuit (IC) comprising a pulse driver, a transmit/receive switch, a wideband low-noise preamplifier, and a line driver is used. By reducing the parasitic capacitance, the use of a custom IC enables pulse-echo measurements at high frequencies with a very small transducer. By comparing frequency response and efficiency of the transducer in conventional and collapse regimes, experimental results show that a collapsed membrane can be used to generate and detect ultrasound more efficiently than a membrane operated in the conventional mode. Furthermore, the center frequency of the collapsed membrane can be changed by varying the applied DC voltage. In this study, the center frequency of a collapsed transducer in immersion is shown to vary from 20 MHz to 28 MHz with applied DC bias; the same transducer operates at 10 MHz in the conventional mode. In conventional mode, the maximum peak-to-peak pressure is 370 kPa on the transducer surface for a 40-ns, 25-V unipolar pulse excitation. In collapse mode, a 25-ns, 25-V unipolar pulse generates 590 kPa pressure at the surface of the transducer.

Use of L-carnitine and humate in laying quail diets.

This experiment was carried out to determine the effects of using L-carnitine and humate alone or in combination in quail diets on laying performance, egg traits and blood parameters. A total of 280 Japanese quails aged 10 weeks, divided into one control group and three treatment groups, were used. The diets of the first, second and third treatment groups were supplemented with 100 mg L-carnitine/kg, 1.5 g humate (Farmagülatör Dry Plus)/kg and 100 mg L-camitine + 1.5 g humate/kg, respectively. The experimental period lasted 16 weeks. The addition of L-carnitine and sodium humate alone or in combination did not significantly affect body weight, feed consumption, egg production, feed conversion ratio, mortality, egg-shell thickness, egg yolk index and the percentages of egg-shell, albumen and yolk. Egg weight increased (P < 0.001) with L-carnitine supplementation. The values of egg albumen height (P < 0.05), egg albumen index (P < 0.01) and egg Haugh unit (P < 0.05) were increased with humate supplementation. Egg cholesterol content and blood serum parameters were not affected by the supplementation of L-carnitine with or without humate. The results in this study demonstrated that L-carnitine supplementation increased egg weight while humate addition increased egg albumen index and egg Haugh unit of laying quails. However, the combined administration of L-carnitine and humate did not have any significant effects on the parameters measured.

Capacitive micromachined ultrasonic transducer design for high power transmission.

Capacitive micromachined ultrasonic transducers (cMUTs) were developed to meet the demands of the ultrasonic industry. To achieve maximum efficiency, the conventional operation of the cMUT requires a bias voltage close to the collapse voltage. Total acoustic output pressure is limited by the efficiency of the cMUT and the maximum-allowed pulse voltage on the membrane. In this paper, we propose the collapse-snapback operation of the cMUT: the membrane is collapsed onto the substrate in the collapsing cycle, and released in the snapback cycle. The collapse-snapback operation overcomes the above-mentioned limitations of the conventional operation. The collapse-snapback operation utilizes a larger range of membrane deflection profiles (both collapsed and released profiles) and generates higher acoustic output pressures. The static finite element calculations were performed to design cMUTs with specific collapse and snapback voltages by changing the electrode parameters (radius (re), position (de), and thickness (te)). These designs were refined for optimum average displacement per cycle. An electrode radius greater than 60% of the membrane radius significantly improved the displacement per volt. Moderately thick membranes (te approximately 0.2 microm) were preferred, as thicker membranes reduced the displacement per volt. Under proper bias conditions, the collapse-snapback operation, designed for high-power transmission, allowed the application of pulse voltages larger than the difference of collapse and snapback voltages. Dynamic finite element calculations of an infinite cMUT array on the substrate loaded with acoustic fluid medium were performed to determine the dynamic response of the cMUT. Commercially available FEM packages ANSYS and LS-DYNA were used for static and dynamic calculations, respectively. The cMUTs were fabricated for optimal performance in the collapse-snapback operation. The transmit experiments were performed on a 2-D cMUT array using a calibrated hydrophone. Taking into account the attenuation and diffraction losses, the pressure on the cMUT surface was extracted. The cMUT generated 0.47 MPa (6 kPa/V) and 1.04 MPa (11 kPa/V) in the conventional and collapse-snapback operations, respectively. Therefore, collapse-snapback operation of the cMUTs was superior for high-power transmission.

Finite-element analysis of capacitive micromachined ultrasonic transducers.

In this paper, we present the results of finite-element analysis performed to investigate capacitive micromachined ultrasonic transducers (CMUTs). Both three-dimensional (3-D) and 2-D models were developed using a commercially available finite-element modeling (FEM) software. Depending on the dimensionality of the model, the membranes were constructed using plane or shell elements. The electrostatic gap was modeled using many parallel plate transducers. An axisymmetric model for a single membrane was built; the electrical input impedance of the device then was calculated in vacuum to investigate series and parallel resonant frequencies, where the input impedance has a minimum and a maximum, respectively. A method for decomposing the membrane capacitance into parasitic and active parts was demonstrated, and it was shown that the parallel resonant frequency shifted down with increased biased voltage. Calculations then were performed for immersion transducers. Acoustic wave propagation was simulated in the immersion medium, using appropriate elements in a 3-D model. Absorbing boundaries were implemented to avoid the reflections at the end of the medium mesh. One row of an array element, modeled with appropriate boundary conditions, was used to calculate the output pressure. The results were compared with a simpler model: a single membrane in immersion, with symmetry boundary conditions on the sidewalls that cause the calculations to reflect the properties of an infinitely large array. A 2-D model then was developed to demonstrate the effect of membrane dimensions on the output pressure and bandwidth. Our calculations revealed that the small signal transmit pressure was inversely proportional to the square root of gap height. We also compared FEM results with analytical and experimental results.

Dynamic analysis of capacitive micromachined ultrasonic transducers.

Electrostatic transducers are usually operated under a DC bias below their collapse voltage. The same scheme has been adopted for capacitive micromachined ultrasonic transducers (cMUTs). DC bias deflects the cMUT membranes toward the substrate, so that their centers are free to move during both receive and transmit operations. In this paper, we present time-domain, finite element calculations for cMUTs using LS-DYNA, a commercially available finite element package. In addition to this DC bias mode, other new cMUT operations (collapse and collapse-snapback) have recently been demonstrated. Because cMUT membranes make contact with the substrate in these new operations, modeling of these cMUTs should include contact analysis. Our model was a cMUT transducer consisting of many hexagonal membranes; because it was symmetrical, we modeled only one-sixth of a hexagonal cell loaded with a fluid medium. The finite element results for both conventional and collapse modes were compared to measurements made by an optical interferometer; a good match was observed. Thus, the model is useful for designing cMUTs that operate in regimes where membranes make contact with the substrate.

Do somatosensory evoked potentials in traumatic brain injury patients indicate brainstem generators for frontally recorded N18, P20 and cervical N13?

PRIMARY OBJECTIVE: To examine the generator of frontal somatosensory evoked potentials by studying patients with traumatic brain injury in the chronic phase. RESEARCH DESIGN: A prospective, non-comparative case series. METHODS AND PROCEDURES: Median nerve somatosensory evoked potentials were performed in 26 survivors of severe traumatic brain injury, which had taken place at a mean of 7 months before. Potentials of short latency somatosensory evoked potentials were recorded simultaneously over the frontal and parietal scalp. MAIN OUTCOMES AND RESULTS: Frontally recorded latencies N18, P20 and N13 recorded from C2 correlated highly significantly with the duration of coma (p<0.01), a history of raised intracranial pressure (p<0.05) and with each other (p<0.01) in traumatic brain injury patients. CONCLUSIONS: These findings indicate that frontally recorded N18, P20 and N13 recorded from C2 are generated in part in the brainstem, which becomes damaged by increased intracranial pressure due to secondary injury in severe traumatic brain injury.