Análisis de los parámetros ecográficos descritos en el estudio del síndrome del túnel del carpo. Una revisión sistemática / Analysis of the echographic parameters described in the study of carpal tunnel syndrome: A systematic review

El síndrome del túnel del carpo (STC) es la mononeuropatía por atrapamiento más frecuente; el diagnóstico se establece mediante pruebas electrodiagnósticas con un número sustancial de falsos positivos/negativos. Presentamos la siguiente revisión sistemática, cuyo objetivo es analizar la literatura más reciente en relación con los parámetros ecográficos descritos para estudiar el STC. Seleccionamos estudios que evaluasen parámetros ecográficos en pacientes con sospecha clínica, siguiendo las recomendaciones del manual Cochrane; incluimos revisiones sistemáticas, metaanálisis, estudios caso-control y de pruebas diagnósticas, valorando estudios retrospectivos y revisiones bibliográficas con buena calidad metodológica. La revisión se hizo de artículos publicados entre 2005-2019. Incluimos 8 artículos (2 revisiones sistemáticas/metaanálisis, 2 estudios caso-control, un estudio de pruebas diagnósticas, 2 revisiones literarias y un estudio retrospectivo). Los parámetros analizados fueron el área de sección transversa del nervio mediano, el índice muñeca-antebrazo, el índice entrada-salida, el rango de adelgazamiento del nervio mediano, el abombamiento del retináculo flexor y la vascularización/movilidad. La evidencia actual permite afirmar que la ecografía tiene utilidad en el cribado del STC.(AU)

Carpal tunnel syndrome (CTS) is the most common entrapment mononeuropathy; the diagnosis is established by electrodiagnostic tests with until 34% of false positives/negatives. We present the following systematic review which objective is to analyze the most recent literature related to the ultrasound parameters described to study CTS. We selected studies that evaluated ultrasound parameters in patients with clinical suspicion following the Cochrane manual's recommendations. We include systematic reviews, meta-analyses, case–control studies and diagnostic tests, evaluating retrospective studies and bibliographic reviews with proper methodological quality. Articles published between 2005 and 2019. We included eight articles (two systematic reviews/meta-analyses, two case–control studies, one diagnostic test study, two literature reviews, and one retrospective). The parameters analyzed were cross-sectional area, wrist–forearm index, entry–exit index, thinning range, palmar bowing of the flexor retinaculum, and vascularity/mobility. Current evidence allows us to affirm that ultrasound is useful in screening for CTS.(AU)

Neuromuscular Ultrasound: Indications in the Electrodiagnostic Laboratory.

ABSTRACT: Accurate assessment of neuromuscular disorders is critical to facilitate timely treatment and achieve the best outcomes. Historically, electrodiagnostic studies have filled this role, but recently, neuromuscular ultrasound is being used in the electrodiagnostic laboratory. This review discusses the uses of neuromuscular ultrasound in the electrodiagnostic laboratory that have strong evidence, emphasizing those that could be adopted in a typical electrodiagnostic laboratory with a reasonable level of equipment and training. The evidence currently supports using neuromuscular ultrasound to diagnose carpal tunnel syndrome and ulnar neuropathies at the elbow and as a supplementary test when electrodiagnostic studies are suspected to be falsely negative or in axonal nonlocalizing lesions. Neuromuscular ultrasound can identify the causes of focal mononeuropathies, which can change treatment in specific cases. It is sensitive at identifying fasciculations and providing complementary evidence of autoimmune demyelinating polyneuropathies. It is particularly helpful in assessing nerves after trauma. Neuromuscular ultrasound is likely to prove even more useful in the electrodiagnostic laboratory as the technology continues to advance.

Sacral dural arteriovenous fistula mimicking multiple mononeuropathy.

A sacral dural arteriovenous fistula (dAVF) is extremely rare, and the pathophysiological and clinical features have not been established. A 70-year-old man developed gradually progressive right-dominant bilateral sensory disorder of the lower limbs. His clinical course and electrophysiological findings were similar to those of multiple mononeuropathy. However, angiography showed a sacral dAVF at the right intervertebral foramen between the fifth lumbar and first sacral vertebrae. Endovascular embolization of the dAVF improved his clinical symptoms and electrophysiological findings. A sacral dAVF can mimic multiple mononeuropathy in terms of its clinical features and electrophysiological findings. A sacral dAVF is a treatable disease and should be considered as a differential diagnosis of lower extremity disorders.

Nerve Ultrasonography as an Additive Tool to Clinical Examination and Electrodiagnostics in Sporadic Mononeuritis - Imaging is the Key.

PURPOSE: Sporadic mononeuropathies without trauma or compression are challenging to diagnose. Nerve ultrasound has recently proven its usefulness in the diagnosis of traumatic neuropathies, tumors and polyneuropathies. However, its role in mononeuropathies currently remains unclear. We describe ultrasonography follow-up results in 12 patients with suggested spontaneous, monophasic mononeuritis without signs of generalization. MATERIALS AND METHODS: Nerve conduction studies (NCS), ultrasonography of the affected nerves and the contralateral side, laboratory analysis, and if possible magnetic resonance imaging (MRI) of the affected nerves were established in all patients at onset. In one patient, additive nerve biopsy was performed. In all patients, ultrasonography was repeated after immunotherapy. RESULTS: An infectious pathogen of neuritis was not found in any patient. All but one patient showed predominant axonal nerve damage in NCS, whereas ultrasonography and MRI revealed fascicular and/or overall cross-sectional area (CSA) enlargement or T2 hyperintensity of the affected nerve segments, suggesting an inflammatory background of the neuropathy. Most patients showed significant clinical amelioration of symptoms under treatment (75.0 %) and consequently a decrease in CSA/fascicle enlargement over time (77.8 %). CONCLUSION: Ultrasonography and MRI of the nerves revealed enlargement in patients with mononeuropathy of axonal NCS pattern of unknown origin. Ultrasonography can facilitate the therapeutic decision for immunotherapy. Next to nerve trauma, nerve tumors and nerve entrapments, ultrasonography reliably shows nerve enlargement in the case of inflammation and therefore could further enrich neurophysiology. Nerve imaging might serve as a follow-up tool by observing a decrease in nerve enlargement and improved function.

Magnetic resonance imaging patterns of mononeuropathic denervation in muscles with dual innervation.

Magnetic resonance imaging (MRI) of mononeuropathy in muscles with dual innervation depicts geographic denervation corresponding to the affected nerve. Knowledge of the normal distribution of a muscle's neural supply is clinically relevant as partial muscle denervation represents a potential imaging pitfall that can be confused with other pathology, such as muscle strain. This article reviews the normal innervation pattern of extremity muscles with dual supply, providing illustrative examples of mononeuropathy affecting such muscles.

Pins and Needles From Fingers to Toes: High-Resolution MRI of Peripheral Sensory Mononeuropathies.

OBJECTIVE: The purpose of this article is to review advanced MRI techniques and describe the MRI findings of pure sensory mononeuropathy with relevant clinical and anatomic correlation. CONCLUSION: Peripheral sensory mononeuropathy can be challenging to evaluate with MRI because of the small caliber of pure sensory nerves and the lack of changes in secondary muscular denervation. Advances in MRI afford the necessary signal-intensity contrast and resolution for adequate evaluation of many of these small peripheral nerves.

The significance of muscle echo intensity on ultrasound for focal neuropathy: The median- to ulnar-innervated muscle echo intensity ratio in carpal tunnel syndrome.

OBJECTIVE: The objective of this study was to investigate the usefulness of muscle ultrasound for evaluating muscle changes caused by denervation in carpal tunnel syndrome (CTS), which is a focal neuropathy. METHODS: The mean and standard deviation (SD) of echo intensity (EI) in the thenar and hypothenar muscles were calculated in 35 patients with CTS and 11 healthy subjects. Patients were assigned to three subgroups based on CTS severity as determined by electrodiagnostic tests. The ratio of thenar muscle pixel brightness to hypothenar muscle pixel brightness was used in statistical analyses. The ratio of mean pixel brightness was termed the EI ratio, and the ratio of the SD of pixel brightness was termed the inhomogeneity ratio. RESULTS: Both the EI ratio and the inhomogeneity ratio were significantly higher in the patient group than in the control group. In a comparison of the three patient subgroups, the severe group showed significant differences in both the EI and inhomogeneity ratios compared to the other two groups. Subjects with denervation potential in the abductor pollicis brevis (APB) had higher EI and inhomogeneity ratios than subjects without denervation potential in the APB. CONCLUSION: The EI ratio and inhomogeneity ratio are useful variables with which to evaluate disease severity and the presence of denervation in patients with CTS. SIGNIFICANCE: Muscle ultrasound has clinical significance in the detection of muscle changes that result from neuropathy.

Ultrasound imaging of the axillary nerve and its role in the diagnosis of traumatic impairment.

PURPOSE: The axillary nerve (AN) is frequently injured during shoulder trauma and imaging is required to define the site and extent of nerve injury. However, the AN has a rather complex course through several soft tissue compartments of the shoulder and axilla. Therefore, imaging of the nerve with MRI and sonography is troublesome. Thus detection and sonographic assessment bases on thorough knowledge of local topography. MATERIALS AND METHODS: This investigation aimed at defining reliable anatomical landmarks for AN-sonography in 5 volunteers and later validating the proposed sonographic examination protocol in 10 unselected patients. RESULTS: With strict adherence to the proposed examination algorithm, sonography of the AN was feasible in all volunteers and patients. Furthermore, sonographic findings correlated nicely with the golden standard "surgical exploration" concerning severity and topography of neural impairment. CONCLUSION: Based on our study results we propose our algorithm for AN-sonography as the first-line imaging tool for the assessment of axillary nerve trauma.

Punched nerve syndrome: ultrasonographic appearance of functional vascular nerve impairment.

PURPOSE: The mechanical impact of a neighboring vessel on a "punched" nerve segment is thought to be one possible cause of compression neuropathy but has not been proven definitively. We report on 9 subjects with unclear clinical mononeuropathies in whom we could clearly define peripheral nerve impairment by such vessels on real-time high-resolution ultrasound (HRUS). MATERIALS AND METHODS: Nine subjects with unclear mononeuropathy based on clinical neurological examination were referred to our department for HRUS assessment. The shape, inner and outer echotexture, size and diameter, and overall integrity of these nerves were assessed including an exact analysis of the surrounding soft tissues to search for potentially extraneural pathology. This included duplex imaging to identify even tiny atypical vascular structures. RESULTS: In all patients duplex HRUS showed the pulsatile and "punching" character of the relevant vessels and the direct mechanical impact of these vessel. The involved nerve segments appeared enlarged with a hypoechoic change of echotexture including at least partial masking of their inner fascicular texture. CONCLUSION: Although rare, a "punching" vessel can be the cause of a compression neuropathy. Therefore, duplex HRUS must be included in every HRUS examination of patients with otherwise unclear mononeuropathy.

Ultrasound diagnosis of peroneal nerve variant in a child with compressive mononeuropathy.

We report on a 6-year-old child presenting with subacute foot drop. Neurophysiologic and radiologic studies revealed a peroneal nerve compression secondary to fibular exostosis. Before undergoing surgical removal of the exostosis, the patient underwent further neurophysiologic and ultrasonographic evaluation that showed the presence of an accessory peroneal nerve branch that caused gastrocnemius involvement. Findings at surgery confirmed the supposed anatomical variant. Both nerve components were carefully preserved during the operative procedure. The association of ultrasonographic and neurophysiologic studies was crucial in identifying the etiopathologic mechanism and anatomical picture and provided clinicians and surgeons with important information in planning the procedure.

Human cerebellar responses to brush and heat stimuli in healthy and neuropathic pain subjects.

Though human pain imaging studies almost always demonstrate activation in the cerebellum, the role of the cerebellum in pain function is not well understood. Here we present results from two studies on the effects of noxious thermal heat and brush applied to the right side of the face in a group of healthy subjects (Group I) and a group of patients with neuropathic pain (Group II) who are more sensitive to both thermal and mechanical stimuli. Statistically significant activations and volumes of activations were defined in the cerebellum. Activated cerebellar structures were identified by colocalization of fMRI activation with the 'MRI Atlas of the Human Cerebellum'. Functional data (obtained using a 3T magnet) were defined in terms of maximum voxels and volume of activation in the cerebellum. Volume maps were then mapped onto two millimeter serial slices taken through the cerebellum in order to identify activation within regions defined by the activation volume. The data indicate that different regions of the cerebellum are involved in acute and chronic pain processing. Heat produces greater contralateral activation compared with brush, while brush resulted in more ipsilateral/bilateral cerebellar activation. Further, innocuous brush stimuli in healthy subjects produced decreased cerebellar activation in lobules concerned with somatosensory processing. The data also suggest a dichotomy of innocuous stimuli/sensorimotor cerebellum activation versus noxious experience/cognitive/limbic cerebellum activation. These results lead us to propose that the cerebellum may modulate the emotional and cognitive experience that distinguishes the perception of pain from the appreciation of innocuous sensory stimulation.

Paraneoplastic mononeuritis multiplex in non-small-cell lung carcinoma.

A 60-year-old man developed two selective peripheral mononeuropathies of the peroneal and later the radial nerve, shortly after a diagnosis of large-cell lung carcinoma. Nerve conduction studies and electromyography confirmed isolated lesions in both nerves, and in the case of the peroneal nerve lesion, focal conduction block was localised to the level of the fibula neck. Subsequent magnetic resonance imaging of the lower limb excluded focal compression or malignant infiltration along the course of the peroneal nerve, and there was no signal change within the nerve, prompting a diagnosis of paraneoplastic mononeuritis multiplex. Anti-neuronal antibodies and serological markers of systemic vasculitis were negative. Neither the patient's large-cell lung carcinoma nor mononeuritis multiplex responded to chemotherapy, and he died within 6 months of the initial diagnosis.