Neurografía por resonancia magnética para la identificación de la neuralgia del nervio pudendo / Magnetic resonance neurography for the identification of pudendal neuralgia

La neuralgia del nervio pudendo (NP) es una entidad poco estudiada por imágenes. Se reconocen varias causas, tales como compresión a través de su paso por estructuras ligamentarias; estiramiento por partos laboriosos; lesiones secundarias a cirugías rectales, perineales, urológicas y ginecológicas, traumatismos con o sin fractura de huesos pelvianos; procesos inflamatorios/autoinmunes; tumores del NP, y, compresión/desplazamiento por tumores o seudotumores de pelvis. El diagnóstico de neuralgia del NP se sospecha por la clínica y se confirma por diferentes métodos, tales como las pruebas electrofisiolológicas: potenciales evocados, test de latencia motora terminal y electromiograma, y, a través de bloqueos neurales y resonancia magnética. La neurografía por resonancia magnética de alta resolución, debería ser empleada como estudio diagnóstico complementario junto a la clínica y exámenes electrofisiológicos, en los pacientes con sospecha de neuralgia del NP.

The pudendal nerve entrapment is an entity understudied by diagnosis imaging. Various causes are recognized in relation to difficult labors, rectal, perineal, urological and gynecological surgery, pelvic trauma fracture, bones tumors and compression by tumors or pelvic pseudotumors. Pudendal neuropathy should be clinically suspected, and confirmed by different methods such as electrofisiological testing: evoked potentials, terminal motor latency test and electromyogram, neuronal block and magnetic resonance imaging. The radiologist should be acquainted with the complex anatomy of the pelvic floor, particularly on the path of pudendal nerve studied by magnetic resonance imaging. High resolution magnetic resonance neurography should be used as a complementary diagnostic study along with clinical and electrophysiological examinations in patients with suspected pudendal nerve neuralgia.

Detecting Peripheral Nerves in the Elbow using Three-Dimensional Diffusion-Weighted PSIF Sequences: a Feasibility Pilot Study

PURPOSE: To analyze the feasibility of three-dimensional (3D) diffusion-weighted (DW) PSIF (reversed FISP [fast imaging with steady-state free precession]) sequence in order to evaluate peripheral nerves in the elbow. MATERIALS AND METHODS: Ten normal, asymptomatic volunteers were enrolled (6 men, 4 women, mean age 27.9 years). The following sequences of magnetic resonance images (MRI) of the elbow were obtained using a 3.0-T machine: 3D DW PSIF, 3D T2 SPACE (sampling perfection with application optimized contrasts using different flip angle evolution) with SPAIR (spectral adiabatic inversion recovery) and 2D T2 TSE (turbo spin echo) with modified Dixon (m-Dixon) sequence. Two observers used a 5-point grading system to analyze the image quality of the ulnar, median, and radial nerves. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of each nerve were measured. We compared 3D DW PSIF images with other sequences using the Wilcoxon-signed rank test and Friedman test. Inter-observer agreement was measured using intraclass correlation coefficient (ICC) analysis. RESULTS: The mean 5-point scores of radial, median, and ulnar nerves in 3D DW PSIF (3.9/4.2/4.5, respectively) were higher than those in 3D T2 SPACE SPAIR (1.9/2.8/2.8) and 2D T2 TSE m-Dixon (1.7/2.8/2.9) sequences (P < 0.05). The mean SNR in 3D DW PSIF was lower than 3D T2 SPACE SPAIR, but there was no difference between 3D DW PSIF and 2D T2 TSE m-Dixon in all of the three nerves. The mean CNR in 3D DW PSIF was lower than 3D T2 SPACE SPAIR and 2D T2 TSE m-Dixon in the median and ulnar nerves, but no difference among the three sequences in the radial nerve. CONCLUSION: The three-dimensional DW PSIF sequence may be feasible to evaluate the peripheral nerves around the elbow in MR imaging. However, further optimization of the image quality (SNR, CNR) is required.

Neurografía por resonancia magnética en la evaluación de los nervios periféricos / Magnetic resonance neurography in the evaluation of peripheral nerves

Magnetic resonance neurography (MRN), with high resolution sequences, allows for a detailed study of the plexus and peripheral nerves. For its interpretation, it is necessary to have a general knowledge of MR, as well as of the anatomy of the neuromuscular system and lesions that affect it. Nerve and plexus pathology can be divided into mononeuropathies (for trauma, entrapment or tumors) and hereditary polyneuropathies (such as Charcot-Marie-Tooth disease) or acquired (for chronic idiopathic demyelinating polyradiculoneuropathy, diabetes, vasculitis or inflammation). The objective of this review is to describe the study technique of Magnetic Resonance Neurography as well as the characteristics of the normal and pathological peripheral nerve.

La neurografía por resonancia magnética (NRM), con secuencias de alta resolución, permite un detallado estudio de los plexos y nervios periféricos. Para su interpretación, es necesario contar con conocimientos generales de RM, así como de la anatomía del sistema neuromuscular y de las lesiones que lo afectan. La patología de los nervios y plexos puede dividirse en mononeuropatías (por trauma, atrapamiento o tumores) y polineuropatías hereditarias (como la enfermedad de Charcot Marie Tooth) o adquiridas (por poliradiculoneuropatía desmielinizante idiopática crónica, diabetes, vasculitis o inflamación) El objetivo de esta revisión es describir la técnica de estudio de la neurografía por resonancia magnética, así como las características del nervio periférico normal y patológico.

Magnetic Resonance Neurography with Short Tau Inversion Recovery Sequences for Cervical Radiculopathy

In magnetic resonance(MR) imagings with short tau inversion recovery(STIR) sequences fat signals are specifically suppressed. These imaging techniques, therefore, have been used to identify optic nerve lesions in the orbits, because there are a lot of fat tissues which may obscure the optic nerves in the orbit. The cervical spinal nerves or ventral primary rami of brachial plexus, during their courses in the necks between anterior and middle scalene muscles, are also surrounded by considerable amount of fat deposits. So we used these MR imaging techniques with already used posterior neck coil system, to image cervical spinal nerves directly, and to know whether there are certain signal changes in those nerves of the involved nerve roots, in 12 patients who were considered to have cervical radiculopathies by conventional diagnostic means. In MR neurography with STIR sequences(STIR MRN) of axial and coronal images, signals of the cervical spinal nerves of the involved roots were detected as fairly bright, and were discerned from signals of the spinal nerves of the uninvolved roots. We also measured contrast-to-noise ratio(CNR) of the spinal nerve signals of the involved and uninvolved roots in axial images. The average CNR value of the former was 4.48+/-0.889 and of the latter 1.40+/-0.274. Our fingings indicate that STIR MRNs can be helpful in limiting the lesions more accurately and in making surgical decisions for cervical radiculopathies caused by multileveled discs or spondylosis.