Dorsal Column Function Research Articles

Comparison of the Interference Effects on Somatosensory Evoked Potential from Tonic, Burst, and High-dose Spinal Cord Stimulations.

Spinal cord stimulations have been used widely to treat intractable neuropathic pain. The conventional spinal cord stimulation paradigm, the “tonic” type, suppresses excessive activation of wide dynamic range neurons in the dorsal horn via the collateral branch from the dorsal column. Therefore, preserved dorsal column function is an important prerequisite for tonic spinal cord stimulations. A tonic spinal cord stimulation requires eliciting paresthesia in the painful area due to stimulation of the dorsal column and dorsal root. Recent spinal cord stimulation paradigms, including burst and high-dose, are set below the paresthesia threshold and are proposed to have different pain reduction mechanisms. We conducted an interference study of these different stimulation paradigms on the somatosensory evoked potential (SEP) to investigate differences in the sites of action between tonic and new spinal cord stimulations. We recorded posterior tibial nerve-stimulated SEP in seven patients with neuropathic pain during tonic, burst, and high-dose stimulations. The total electrical energy delivered was calculated during SEP-spinal cord stimulation interference studies. High-dose stimulations could not reduce the SEP amplitude despite higher energy delivery than tonic stimulation. Burst stimulation with an energy similar to the tonic stimulation could not reduce SEP amplitude as tonic stimulation. The study results suggested different sites of action and effects on the spinal cord between the conventional tonic and burst or high-dose spinal cord stimulations.

Sudden-onset dizziness and vertigo symptoms: assessment and management of vestibular causes.

Approximately 2% of adults seek medical attention annually for symptoms of moderate to severe dizziness, with a third of consultations attributable to a vestibular cause.1 Aside from the healthcare burden, there are significant socioeconomic implications for patients presenting with these symptoms. The diagnosis can be challenging given the wide range of possible causes — both vestibular and non-vestibular (see this graphically online at www.balancedisorderspectrum.info).2 The four most common vestibular diagnoses causing sudden-onset dizziness will be reviewed in detail. These are vestibular neuritis (or neuronitis) (VN), benign paroxysmal positional vertigo (BPPV), vestibular migraine (VM), and Meniere’s disease. Both vestibular and non-vestibular causes of dizziness are listed (Supplementary Table 1) but this is not exhaustive. A detailed history (Supplementary Table 1) can diagnose the majority of both vestibular and non-vestibular causes. A detailed neuro-otological examination should be undertaken including otoscopy, cranial nerve examination, HINTS examination (Supplementary Table 2), Romberg’s (test of proprioception and dorsal column function) and Unterberger’s test (as per Romberg’s but with the patient marching on the spot, rotating towards side of vestibular hypofunction), and a lying and standing blood pressure reading. Dix–Hallpike testing can be used to diagnose BPPV. Presence of geotropic (beating towards the ground), torsional nystagmus on Dix–Hallpike testing supports a diagnosis of BPPV and can be followed by a therapeutic Epley manoeuvre. The main concern here is not missing a cerebellar vascular event involving the anterior or …

The Graph-DCK Scale: a measure of dorsal column function after spinal cord injury.

Cohort/psychometric study. Assessment of dorsal column medial lemniscus (DCML) function is important for the clinical evaluation of people with spinal cord injury (SCI) because it provides useful information to guide rehabilitation and for prognosticating outcomes. For example, research suggests that damage to the DCML pathway may be associated with neuropathic pain after SCI. Tests for graphesthesia and directional cutaneous kinesthesia (DCK) are commonly used clinically to assess DCML function. However, the reliability and validity of these assessments in people with SCI have not been investigated. Moreover, there is a poor consistency between studies in the methodology of graphesthesia and DCK assessment. The purpose of this study was to determine the psychometric properties of the Graph-DCK Scale, which is a simple and potentially useful scale for assessing graphesthesia and DCK. The Graph-DCK Scale does not require expensive equipment and it takes less than 5 min to administer. A university-based laboratory in Miami, FL, USA. Sixty-seven people with chronic SCI and neuropathic pain were included in this study. The Graph-DCK Scale and vibration detection were measured twice in each participant, with a two- to four-week period between measurement sessions. The scale demonstrated an excellent internal consistency (Cronbach's alpha > 0.90) and test-retest reliability (ICC values > 0.80). Further, convergent validity was supported by moderate and significant positive correlations to vibration detection (r values > 0.40). The Graph-DCK Scale is quick and easy to administer, and it provides a reliable and valid assessment of DCML function in people with SCI. Craig Neilsen Foundation.

Spinal cord infarction: Clinical and imaging insights from the periprocedural setting

ObjectiveDescribe the range of procedures associated with spinal cord infarction (SCI) as a complication of a medical/surgical procedure and define clinical and imaging characteristics that could be applied to help diagnose spontaneous SCI, where the diagnosis is often less secure. MethodsWe used an institution-based search tool to identify patients evaluated at Mayo Clinic, Rochester, MN from 1997 to 2016 with a periprocedural SCI. We performed a descriptive analysis of clinical features, MRI and other laboratory findings, and outcome. ResultsSeventy-five patients were identified with SCI related to an invasive or non-invasive surgery including: aortic aneurysm repair (49%); other aortic surgery (15%); and a variety of other procedures (e.g., cardiac surgery, spinal decompression, epidural injection, angiography, nerve block, embolization, other vascular surgery, thoracic surgery) (36%). Deficits were severe (66% para/quadriplegia) and maximal at first post-procedural evaluation in 61 patients (81%). Impaired dorsal column function was common on initial examination. Imaging features included classic findings of owl eyes or anterior pencil sign on MRI (70%), but several other T2-hyperintensity patterns were also seen. Gadolinium enhancement of the SCI and/or cauda equina was also common when assessed. Six patients (10%) had an initial normal MRI despite a severe deficit. ConclusionsProcedures associated with SCI are many, and this complication does not exclusively occur following aortic surgery. The clinical and radiologic findings that we describe with periprocedural SCI may be used in future studies to help distinguish spontaneous SCI from alternate causes of acute myelopathy.

Intrathecal Acetyl-L-Carnitine Protects Tissue and Improves Function after a Mild Contusive Spinal Cord Injury in Rats.

Primary and secondary ischemia after spinal cord injury (SCI) contributes to tissue and axon degeneration, which may result from decreased energy substrate availability for cellular and axonal mitochondrial adenosine triphosphate (ATP) production. Therefore, providing spinal tissue with an alternative energy substrate during ischemia may be neuroprotective after SCI. To assess this, rats received a mild contusive SCI (120 kdyn, Infinite Horizons impactor) at thoracic level 9 (T9), which causes loss of ∼ 80% of the ascending sensory dorsal column axonal projections to the gracile nucleus. Immediately afterwards, the energy substrate acetyl-L-carnitine (ALC; 1 mg/day) or phosphate-buffered saline (PBS) was infused intrathecally (sub-arachnoid) for 6 days via an L5/6 catheter attached to a subcutaneous Alzet pump. ALC treatment improved overground locomotor function (Basso-Beattie-Breshnahan [BBB] score 18 vs. 13) at 6 days, total spared epicenter (71% vs. 57%) and penumbra white matter (90% vs. 85%), ventral penumbra microvessels (108% vs. 79%), and penumbra motor neurons (42% vs. 15%) at 15 days post-SCI, compared with PBS treatment. However, the ascending sensory projections (anterogradely traced with cholera toxin B from the sciatic nerves) and dorsal column white matter and perfused blood vessels were not protected. Furthermore, grid walking, a task we have shown to be dependent on dorsal column function, was not improved. Thus, mitochondrial substrate replacement may only be efficacious in areas of lesser or temporary ischemia, such as the ventral spinal cord and injury penumbra in this study. The current data also support our previous evidence that microvessel loss is central to secondary tissue degeneration.

Case report from the NIH Clinical Center: CNS nocardiosis

Case report from the NIH Clinical Center: CNS nocardiosis

Epicritic Sensation in Cervical Spinal Cord Injury: Diagnostic Gains Beyond Testing Light Touch

Abstract Applied as a bedside test of gross dorsal column function, the testing of light touch (LT) sensation is of high clinical value in the diagnosis of human spinal cord injury (SCI). However, the assessment of overall dorsal column deficit by testing only LT may be limited, because the dorsal column pathway conveys several large diameter afferent modalities (e.g., sensation of touch, two-point discrimination, and proprioception). Therefore, the objective of this study was to compare the epicritic sensation assessed by LT, Semmes-Weinstein monofilament (SWM), and electrical perception threshold (EPT) across cervical dermatomes (C3-C8) in individuals with cervical SCI. A multicenter cross-sectional study was performed at 6 months after cervical SCI, applying combined measures of LT, SWM, and EPT, bilaterally over predefined key sensory points (C3-C8). A total of 300 left- and right-sided dermatomes were tested for each outcome measure in 25 participants. The percentage agreement between classifications according to LT and SWM/EPT testing for all dermatomes between C3 and C8 ranged from 95.5% to 36.2%. The degree of agreement showed considerably variable κ coefficients (-0.1≥kw≤0.7) for each dermatome between C3 and C8. The additional measurements of epicritic sensation by SWM and EPT increased sensitivity by detecting and quantifying differences in sensory thresholds above, at, and below the LT level of injury. This is relevant for early clinical trials (phase 1/2), in which disclosing any biological activity of an intervention may be revealed by subtle sensory changes that might gain a clinical relevance.

Evolving Compartment Syndrome Detected by Loss of Somatosensory- and Motor-evoked Potential Signals During Cervical Spine Surgery

Neurologic injury is a rare but devastating complication of spinal surgery that can result in mild sensory to severe motor deficits. Surgeons increasingly use electrophysiological spinal cord function monitoring, including somatosensory- and motor-evoked potentials, intraoperatively to provide information about spinal cord function, aid in surgical decision making, improve outcomes, and reduce complication rates. By providing real-time information about the dorsal and anterior motor column function, somatosensory- and motor-evoked potentials signals allow surgeons to reverse noticeable changes and avoid devastating neurologic injuries. Recognizing changes in baseline signals in the setting of known risk factors enables surgeons to correct these risks. This article describes a case in which somatosensory- and motor-evoked potentials monitoring were lost in the setting of an impending right forearm compartment syndrome during 2-level anterior cervical diskectomy and fusion. To the authors' knowledge, this is the first reported case of spinal cord monitoring detecting an evolving compartment syndrome during cervical spine surgery. The early changes in signal intensity enabled the surgeon to search for a cause and remedy the situation by removing the infiltrated intravenous line. Without the observed changes in somatosensory- and motor-evoked potentials, it is likely that the compartment syndrome may have progressed to the point of requiring fasciotomy to prevent lasting neuromuscular injury. This article describes a new cause of changes in electrophysiological monitoring and further displays the usefulness of somatosensory- and motor-evoked potentials monitoring during even routine spinal surgery.

Role of Diffusion MRI in Diagnosis of Spinal Cord Infarction in Children

Anterior spinal artery (ASA) infarction is a rare but well-described cause of flaccid paraparesis in adults, presenting with a high thoracic spinothalamic sensory level and preservation of dorsal column function. Careful sensory examination, demonstrating loss of spinothalamic modalities with preservation of dorsal column modalities, supports a clinical diagnosis of ASA infarction. Findings on conventional MRI of the spinal cord are often non-specific, and diffusion-weighted imaging (DWI) is not routinely performed. We describe four children with ASA infarction after minor trauma. DWI was performed in all cases and confirmed the clinical diagnosis.

Intraoperative Motor Evoked Potentials

ABSTRACT.Motor impairment is among the most feared and devastating outcomes following major surgery. Traditionally, the “wake-up test” has been used for intraoperative evaluation of motor function, but is associated with a number of limitations such as its general crudeness, common anesthetic risks such as extubation and recall, inadequacy as a continuous neuromonitoring technique, and lack of clinical utility with a neurologically uncooperative patient. Various neurophysiological monitoring techniques have been championed as alternatives. Although intraoperative neuromonitoring of dorsal column function using somatosensory evoked potentials (SSEPs) has been well established and routinely used for over 20 years during spinal surgeries, selective injury to the anterior spinal cord and its motor pathways can go undetected. Because of the distinct differences in blood supply to the dorsal and ventral aspects of the spinal cord and since somatosensory evoked potentials do not directly monitor the motor pathways, a number of other neurophysiological techniques have been recently developed for intraoperative monitoring of motor pathway integrity. These techniques have involved either direct or indirect stimulation of the spinal cord rostral to the site of surgery, and transcranial magnetic or electrical stimulation of the motor cortex. Distal recording sites have included the spinal cord, cauda equina, peripheral nerves, and muscles of the upper and lower extremities. For most of the spinal cord stimulation techniques, considerable controversy exists over the neural composition of the waveform that is recorded and referred to as a “motor evoked potential (MEP).” A review of these protocols is presented: highlighting the historical background, critically comparing methods, and summarizing optimal intraoperative neuromonitoring strategies.

Ambulatory labour analgesia

The excellent editorial by Dr Bogod (Bogod. Anaesthesia 1999; 54: 1025–7) on maternal mortality in contemporary Africa serves as a timely reminder as we approach the end of this century of the enormous progress that has been achieved in this country in improving the safety of pregnancy and childbirth. In an increasingly consumer-orientated society, we are in danger of taking these massive improvements for granted. That unsupervised, unmedicalised pregnancy and childbirth naturally tend to kill and injure some women and babies is an uncomfortable fact of life, which we would all do well to remember. The fact that we can now engage in the almost superfluous debate about whether women in labour should walk or not is testament enough to the safety and luxury afforded to every child-bearing woman in this country. It is therefore astonishing that Drs Plaat and Razzaque (Razzaque. Anaesthesia 1999; 54: 1118) should seek to defend their routine use of the CSE in labour on the grounds that women should be allowed to walk simply because they might wish to do so. Has the CSE in labour been so discredited that its advocates now have to invoke the defence of consumer rights to justify its continued use? Has the CSE been relegated to the status of lifestyle accessory for some women? There can be little doubt that the CSE has failed to fulfil initial expectations, that by facilitating ambulation it would improve the outcome of labour. Many studies show no difference in maternal satisfaction for analgesia when the CSE is compared with either low- or high-dose epidural analgesia [1-3]. Whilst it appears that women approve of retention of leg power for longer in labour with the CSE, Collis et al. [1] in fact showed that overall maternal satisfaction was related to the quality of analgesia and not to the absence of motor block during labour. Several studies show low rates of ambulation in labour with the CSE; Collis et al. [4] recorded only 24% of women walking about. In another study comparing CSE with high-dose epidural analgesia, Collis et al. [1] again reported that only 24% of women got out of bed for more than a quarter of the block time, and that only 30% of CSE women got out of bed for a ‘short period’, which the authors incidentally fail to define. The most recently published study by Collis et al. [5] implies that ambulation is safe simply because there are few reports of women falling over! How did they intend to adequately evaluate safety on this criterion alone? Dr Plaat is wrong in stating that ambulation with the CSE in labour is safe. The study by Fernando et al. [6] using computerised dynamic posturography provides no evidence that the CSE is safe in labour. The CSE subjects in that study received only the spinal component of the CSE, namely 25 µg fentanyl plus 2.5 mg bupivacaine. They were not tested again later in labour when they would have had several epidural top-ups. Epidural dosing with bupivacaine is known to cause dorsal column impairment [7]. As has been argued elsewhere [8], the time course of the progression of dorsal column dysfunction in labour after CSE or epidural analgesia has not been defined and the safety of continued ambulation has not been conclusively demonstrated. Relying on a woman's own assessment of her ability to walk in the absence of any objective clinical assessment is perhaps taking the spirit of woman-centred delivery just a little bit too far. It behoves us to wait until more definitive studies of dorsal column function are performed before launching our women down the delivery suite corridor on a long and dangerous journey into the unknown.

Estimation of cervical cord dysfunction by somatosensory evoked potentials.

The purpose of this study was to examine the relationship of abnormal short-latency somatosensory evoked potentials (SSEPs) recorded by a noncephalic reference montage with clinical variables in cervical myelopathy patients and to reexamine the diagnostic utility of SSEPs in such patients. We studied cervical SSEPs elicited by stimulating the median and ulnar nerves in 87 patients. Our grade classification of spinal N13, which is based on the normal limits of latencies or amplitudes, corresponded well with the clinical variables and is of value when trying to localize the cervical lesion segmentally. The N9-P14 interpeak latency in response to ulnar nerve stimulation correlated well with lower extremity function (r = -0.440, P <0.0001). We suggest a combined assessment of N13 amplitude, and N9-N13 and N9-P14 interpeak latencies to estimate dorsal column and dorsal horn function separately in patients with cervical myelopathy.

The 29th Annual Meeting of SOAP

The 29th Annual Meeting of SOAP

28th Annual Meeting of the Society for Obstetric Anesthesia and Perinatology

28th Annual Meeting of the Society for Obstetric Anesthesia and Perinatology

Electrophysiological study of dorsal column function in streptozocin-induced diabetic rats: comparison with 2,5-hexanedione intoxication

Dorsal column function and peripheral motor and sensory conduction velocities (MCV, SCV) were evaluated in experimental diabetic rats and compared with those in 2,5-hexanedione (2,5-HD) intoxicated rats. Hyperglycemia was induced by a single injection of streptozocin, and electrophysiological studies were performed 4 and 12 weeks after the injection. For 8 weeks 2,5-HD was administered daily by drinking water to make the 2,5-HD neuropathy rats. Age-matched rats were used as control. In diabetic rats, gracile surface potentials evoked by electrical stimulation of the lumbosacral trunk remained normal during the experimental period, whereas the N and P waves of the evoked potentials were suppressed and the duration of the N wave was prolonged in the 2,5-HD rats. In 4-week diabetic rats, the antidromic compound action potentials of the gracile tract recorded at the most proximal site of lumbosacral trunk were normal. In 12-week diabetic rats, the gracile tract conduction velocity (GTCV) was decreased, although the duration of these potentials was normal. By contrast, the GTCV was decreased and the duration was markedly prolonged in 2,5-HD rats. These findings might indicate that temporal dispersion of incoming volleys in the gracile tract is increased in 2,5-HD rats, but not in diabetic rats. These results suggest that diabetic myelopathy exists that but the magnitude and progression of this condition are quite different from those of 2,5-HD intoxication, typical dying-back-type neuropathy and that the dorsal column is less vulnerable than the peripheral nerve in diabetes mellitus.

Clinical correlates of sway in elderly people living at home.

Postural sway has been noted to increase with advancing age and to correlate with a wide variety of clinical features. The relationships between sway and various clinical features were explored in a group of elderly subjects living at home and free from neurological illness and severe incapacity. Each subject underwent a thorough physical examination and sway was measured in the anteroposterior and lateral planes with eyes open and closed using a modified Wright's ataxiameter. Vibration sense was the only clinical feature to show a consistent relationship with all 4 measurements of sway in men. Age showed only a weak and inconsistent relationship to sway in both men and women. Weak but inconsistent relationships were noted between sway and mental function, tone, passive joint movement, antidepressant and tranquilliser therapy. This suggests that dorsal column function is of prime importance in the maintenance of balance and that the previously noted increase in postural sway with advancing age may have been exaggerated by the presence of disease processes.

Intra-operative recording of cortical somatosensory evoked potentials as a method of spinal cord monitoring during spinal surgery.

The experience with cortical somatosensory evoked potential (SEP) recording during 13 cases of spinal neurological surgery is described. Good quality cortical SEPs were obtained in eight patients with a variety of intradural and extradural spinal disorders. The short latency components of these waveforms were stable during anaesthesia with nitrous oxide, 0.5% halothane and fentanyl. Fluctuations in signal amplitude were, however, common. In the one patient in whom the cortical SEP waveform was distorted intra-operatively, there was an increased neurological deficit. In one normal and four patients with impairment of dorsal column function, no intra-operative cortical SEP was recorded. In these five patients spinal SEPs were recorded rostral to the level of spinal disease. Monitoring spinal cord function using cortical SEPs can provide useful neurophysiological information, however, there are limitations to its utility. These relate to difficulties in signal acquisition, the low signal amplitude, attenuation of the signal during intramedullary surgery and uncertainties in signal interpretation. All these problems are exacerbated if the patient has a pre-operative clinical somatosensory deficit. Although most of these problems can be overcome using spinal SEP monitoring, intra-operative SEP recordings are not an infallible guide to spinal cord integrity since they reflect the functional status of only the dorsal column-medial lemniscus pathway.

Management of bilateral locked facets of the cervical spine.

The management of 15 cases of bilateral locked facets of the cervical spine is reviewed. The C-6, C-7 interspace was the most common interspace involved. There were 4 females and 11 males who were 16 to 63 years old (average, 26 years). Thirteen patients had a complete spinal cord lesion with loss of function below the level of the locked facets. Two had intact dorsal column function. One patient had an ascending spinal cord deficit, which did not change after open reduction. The remainder had no change in spinal cord function after reduction. However, after reduction, 1 patient had a transient root deficit and 2 patients improved in the function of the involved roots. Closed reduction was accomplished by (a) skeletal traction and weight application, (b) manual reduction under sedatives, or (c) manual reduction under general anesthesia. Five patients required open reduction. The failure of closed reduction was attributed to accompanying fractures of one of the facets in 2 cases, increasing neurological deficits during traction in 2 cases, and associated higher cervical fractures in 1 case. Internal stabilization with wire and bone or external stabilization with a halo vest or a brace was used. Twelve patients were followed for 1 1/2 to 7 years (average, 2.7 years). Stabilization after reduction was successful irrespective of the methods used. The various methods of reduction and stabilization are reviewed and discussed.

Projections of cervicothoracic dorsal roots to the cuneate nucleus of the rat, with observations on cellular "bricks".

AbstractThe distribution of cervicothoracic (C1–T2) dorsal roots to the cuneate and accessory cuneate nuclei was studied in the rat with the Fink‐ Heimer I technique following single extradural rhizotomies. Cytoarchitectural analysis of the cuneate nucleus revealed an anatomically distinct caudal and rostral region. The caudal region was characterized by discrete aggregates of cells arranged as “slabs” or “bricks” which continue vertically almost to the ventral limit of the cuneate nucleus. In contrast, the cells of the rostral region were organized in a non‐focal manner.The projection of the cervicothoracic dorsal roots to the cuneate nucleus reflected the cytoarchitectural pattern observed; non‐focal terminal fields of degeneration in the rostral region and discrete “terminal field bands” of degeneration isolated from one another by degeneration‐free zones in the caudal region. However, the projections of dorsal roots C5 and T2 to the caudal region is non‐focal.In both regions of the cuneate nucleus, the distribution of dorsal root degeneration was topographically organized with cranial roots terminating ventrolaterally and more caudal roots, dorsomedially. The amount of intersegmental overlap of dorsal root terminal fields was greater in the rostral than in the caudal region.Individual dorsal roots projected differentially to the two regions of the cuneate nucleus. Roots C3 and C4 distributed primarily to the rostral region whereas C5 to T1 distributed to both regions. T2 root projected primarily to the caudal region. Dorsal roots C1 and C2 did not terminate in either region of the cuneate nucleus.All roots studied projected heavily and topographically to the accessory cuneate nucleus. Extensive overlap of the very dense terminal fields characterized the dorsal root projections to the accessory cuneate nucleus.On the basis of cytoarchitectonics and dorsal root projections, a dual organization of the cuneate nucleus was revealed. This organization reflected previous anatomical and electrophysiological studies in the rat and paralleled the organization described in the dorsal column nuclei of the cat. The significance of the dual organization with respect to dorsal column function was discussed, as was the finding of the lack of C1 and C2 dorsal root projections to the cuneate nucleus.

SLOW POTENTIAL WAVES PRODUCED IN THE CUNEATE NUCLEUS BY CUTANEOUS VOLLEYS AND BY CORTICAL STIMULATION.

SLOW POTENTIAL WAVES PRODUCED IN THE CUNEATE NUCLEUS BY CUTANEOUS VOLLEYS AND BY CORTICAL STIMULATION.