MRI neurography and diffusion tensor imaging of a sciatic perineuroma in a child

Management of Traumatic Trigeminal and Facial Nerve Injuries

In the area of craniomaxillofacial trauma, neurosensory disturbances are encountered commonly, especially with regard to the trigeminal and facial nerve systems. This article reviews the specific microanatomy of both cranial nerves V and VII, and evaluates contemporary neurosensory testing, current imaging modalities, and available nerve injury classification systems. In addition, the article proposes treatment paradigms for management of trigeminal and facial nerve injuries, specifically with regard to the craniomaxillofacial trauma setting.

Diffusion tensor imaging and tractography of the sciatic and femoral nerves in healthy volunteers at 3T

Background

The aim was to clarify the normal fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values of the sciatic and femoral nerves at the level of the hip joint and to visualize the neural tracts with diffusion tensor imaging (DTI).

Methods

Twenty-four healthy volunteers (12 men and 12 women, age 20–29 years) underwent DTI for visualization with tractography and quantification of FA and ADC values on a 3 Tesla MRI (b value = 800 s/mm², motion probing gradient, 11 directions, time to repeat/echo time = 9000/72.6 ms, axial slice orientation, slice thickness = 3.0 mm with no inter-slice gap, field of view = 320 × 320 mm, 96 × 192 matrix, 75 slices, number of acquisitions = 4). Regions of interest in the sciatic nerve were defined at the femoral head, the S1 root, and the midpoint levels. The femoral nerve was evaluated at 3–4 cm proximal to the femoral head level.

Results

The tractography of the sciatic and femoral nerves were visualized in all participants. The mean FA values of the sciatic nerve were increased distally from the S1 root level, through the midpoint, and to the femoral head level (0.314, 0.446, 0.567, p = 0.001, respectively). The mean FA values of the femoral nerve were 0.565. The mean ADC values of the sciatic nerves were significantly lower in the S1 root level than in the midpoint and the femoral head level (1.481, 1.602, 1.591 × 10⁻³ × 10⁻³ mm²/s, p = 0.001, respectively). The ADC values of the femoral nerve were 1.439 × 10⁻³ mm²/s. FA and ADC values showed moderate to substantial inter- and intra-observer reliability without significant differences in gender or laterality.

Conclusion

Visualization and quantification of the sciatic and femoral nerves simultaneously around the hip joint were achieved in healthy young volunteers with DTI. Clinical application of DTI is expected to contribute to hip pain research.

MRI-guided focused ultrasound ablation of lumbar medial branch nerve: Feasibility and safety study in a swine model

PURPOSE

About 10-40% of chronic low back pain cases involve facet joints, which are commonly treated with lumbar medial branch (MB) radiofrequency neurotomy. Magnetic resonance imaging-guided focused ultrasound (MRgFUS), a non-invasive, non-ionising ablation modality used to treat tumours, neuropathic pain and painful bone metastasis can also be used to disrupt nerve conduction. This work's purpose was to study the feasibility and safety of direct MRgFUS ablation of the lumbar MB nerve in acute and subacute swine models.

MATERIALS AND METHODS

In vivo MRgFUS ablation was performed in six swine (three acute and three subacute) using a clinical MRgFUS system and a 3-T MRI scanner combination. Behavioural assessment was performed, and imaging and histology were used to assess the treatment.

RESULTS AND CONCLUSIONS

Histological analysis of the in vivo studies confirmed thermal necrosis of the MB nerve could be achieved without damaging the spinal cord or adjacent nerve roots. MRgFUS did not cause changes in the animals' behaviour or ambulation.

MRI of intraneural perineurioma of the brachial plexus

Intraneural perineurioma is an uncommon benign tumor of the perineurium of peripheral nerve sheaths occurring primarily in adolescents or young adults. MRI is a valuable tool in suggesting this diagnosis and in surgical planning. We report an 18-year old female with progressive right-hand weakness, numbness, and severe atrophic changes of the hand secondary to an intraneural perineurioma involving the right brachial plexus, in whom the initial diagnosis was suggested by MRI.

Diffusivity measurements differentiate benign from malignant lesions in patients with peripheral neuropathy or plexopathy

BACKGROUND AND PURPOSE

Peripheral nerve disorders caused by benign and malignant primary nerve sheath tumors, infiltration or compression of nerves by metastatic disease, and postradiation neuritis demonstrate overlapping features on conventional MR imaging but require vastly different therapeutic approaches. We characterize and compare diffusivities of peripheral nerve lesions in patients undergoing MR neurography for peripheral neuropathy or brachial or lumbosacral plexopathy.

MATERIALS AND METHODS

Twenty-three patients, referred for MR neurography at our institution between 2003 and 2009 for a peripheral mononeuropathy or brachial or lumbosacral plexopathy and whose examinations included DWI, received a definitive diagnosis, based on biopsy results or clinical and imaging follow-up, for a masslike or infiltrative peripheral nerve or plexus lesion suspicious for tumor. Mean ADC values were determined within each lesion and compared across 3 groups (benign lesions, malignant lesions, and postradiation changes).

RESULTS

Both ANOVA and Kruskal-Wallis tests demonstrated a statistically significant difference in ADC values across the 3 groups (P = .000023, P = .00056, respectively). Post hoc pair-wise comparisons showed that the ADC within malignant tumors differed significantly from that within benign tumors and postradiation changes. ADC within benign tumors and postradiation changes did not differ significantly from each other.

CONCLUSIONS

DWI may be highly effective for the differentiation of benign from malignant peripheral nerve masslike or infiltrative lesions.

Intraneural perineurioma of the sciatic nerve: an under-recognized nerve neoplasm with characteristic MRI findings

Intraneural perineurioma is a benign peripheral nerve neoplasm that typically affects teenagers and young adults and tends to result in a motor-predominant neuropathy. The lesion is rare, but has likely been underdiagnosed due to a lack of familiarity among both clinicians and radiologists. There have been few reports in the radiology literature despite the lesion having a fairly characteristic imaging appearance. We report a case of a 26-year-old woman with an intraneural perineurioma of the left sciatic nerve confirmed with excisional biopsy and pathologic analysis.

Localized hypertrophic neuropathy of the sciatic nerve in children: MRI findings

BACKGROUND

Localized hypertrophic neuropathy (LHN) of the sciatic nerve in children is a rare condition characterized by a painless neurological deficit in the sciatic nerve territory.

OBJECTIVE

To demonstrate the role of MRI using a specific protocol and describe the primary findings in LHN.

MATERIALS AND METHODS

Imaging in four children (age 2 years to 12 years) is presented. All children presented with lower limb asymmetry. Three had a steppage gait. LHN was confirmed by electrophysiological studies and by MRI of the whole sciatic nerve with a dedicated protocol covering the lumbar spine and the lower limb.

RESULTS

There were four direct MRI findings: (1) linear and focal hypertrophy with progressive enlargement of a peripheral nerve or plexus diameter, (2) abnormal hyperintensity of the nerve on T2-weighted images, (3) preserved fascicular configuration, and (4) variable enhancement after intravenous gadolinium administration. In addition there were atrophy and fatty infiltration of innervated muscles. MRI was helpful for determining the extent of lesions and in excluding peripheral nerve compression or tumour.

CONCLUSION

MRI of the whole sciatic nerve is the method of choice for diagnosing LHN of the sciatic nerve.

Review of the principal extra spinal pathologies causing sciatica and new MRI approaches

In this paper we illustrate the principal extraspinal pathologies causing sciatica and new approaches for the study of structures such as the lumbosacral plexus (LSP). Visualisation of the LSP in its entirety is difficult with conventional two-dimensional MRI sequences owing to its oblique orientation. In our institution, we have found that the utilisation of three-dimensional short tau inversion-recovery sampling perfection with application-optimised contrasts using different flip angle evolutions sequence is helpful, allowing multiplanar and maximum intensity projection reconstructions in the coronal oblique plane and curvilinear reformats through the plexus. Diffusion tensor imaging enables the observation of microstructural changes and can be useful in surgical planning. The normal anatomy of the LSP, its different extraspinal pathologies and differential diagnoses are thoroughly presented.

Peripheral tumor and tumor-like neurogenic lesions

Neoplasms of neurogenic origin account for about 12% of all benign and 8% of all malignant soft tissue neoplasms. Traumatic neuroma, Morton neuroma, lipomatosis of a nerve, nerve sheath ganglion, perineurioma, benign and malignant peripheral nerve sheath tumors (PNST) are included in this group of pathologies. Clinical and radiologic evaluation of patients with neurogenic tumors and pseudotumors often reveals distinctive features. In this context, advanced imaging techniques, especially ultrasound (US) and magnetic resonance (MR) play an important role in the characterization of these lesions. Imaging findings such as location of a soft tissue mass in the region of a major nerve, nerve entering or exiting the mass, fusiform shape, abnormalities of the muscle supplied by the nerve, split-fat sign, target sign and fascicular appearance should always evoke a peripheric nerve sheath neoplasm. Although no single imaging finding or combination of findings allows definitive differentiation between benign from malign peripheric neurogenic tumors, both US and MR imaging may show useful features that can lead us to a correct diagnosis and improve patient treatment. Traumatic neuromas and Morton neuromas are commonly associated to an amputation stump or are located in the intermetatarsal space. Lipomatosis of a nerve usually appears as a nerve enlargement, with thickened nerve fascicles, embedded in evenly distributed fat. Nerve sheath ganglion has a cystic appearance and commonly occurs at the level of the knee. Intraneural perineuroma usually affects young people and manifests as a focal and fusiform nerve enlargement. In this article, we review clinical characteristics and radiologic appearances of these neurogenic lesions, observing pathologic correlation, when possible.

Look for the nerves! MR neurography adds essential diagnostic value to routine MRI in pediatric practice: a pictorial overview

PURPOSE

This study aimed to assess the feasibility of magnetic resonance (MR) neurography in children, and the potential roles of diffusion-weighted imaging (DWI) and fiber-tracking (FT) techniques.

METHODS

Five pediatric patients (age range: 6-12 years) underwent magnetic resonance imaging (MRI) for various clinical indications: neurogenic bladder (case 1); persistent hand pain following minor trauma (case 2); progressive atrophy of the lower left extremity muscles (case 3); bilateral hip pain (case 4); and palpable left supraclavicular mass (case 5). All studies were performed using a 1.5-T Avanto MRI scanner (Siemens, Erlangen, Germany). The protocol included 3D T2-weighted STIR and SPACE imaging, T1-weighted fat-saturation post-gadolinium imaging and diffusion tensor imaging (DTI) with tractography. ADC (N×10(-3) mm(2)/s) and FA values were calculated from regions of interest (ROIs) centered on the nerves. Nerve-fiber tracks were calculated using a fourth-order Runge-Kutta algorithm (NeuroD software).

RESULTS

MR neurography allowed satisfactory visualization of all neural structures, and FA and ADC measurements were feasible. The final diagnoses were Tarlov cysts, median-nerve compression, sciatic perineurioma, Charcot-Marie-Tooth disease and plexiform neurofibroma in a patient with NF-1.

DISCUSSION

FA and ADC measurements are of little value because of the lack of normal reference values. Nerve-fiber tractography (FT) may be of value in the characterization of tumor pathology, and is also helpful in the planning of surgical treatments.

CONCLUSION

MR neurography is feasible in pediatric patients. However, a considerable amount of work has yet to be done to establish its role in the clinical management of the wide range of peripheral nerve diseases.

Diffusion tensor imaging of peripheral nerves

Magnetic resonance diffusion tensor imaging (DTI) allows the directional dependence of water diffusion to be studied. Analysis of the resulting image data allows for the determination of fractional anisotropy (FA), apparent diffusion coefficient (ADC), as well as allowing three-dimensional visualization of the fiber tract (tractography). We visualized the ulnar nerve of ten healthy volunteers with DTI. We found FA to be 0.752 ± 0.067 and the ADC to be 0.96 ± 0.13 × 10(-3) mm(2)/s. A nuts-and-bolts description of the physical aspects of DTI is provided as an educational process for readers.

High-resolution MR neurography of diffuse peripheral nerve lesions

High-resolution MR imaging of peripheral nerves is becoming more common and practical with the increasing availability of 3T magnets. There are multiple reports of MR imaging of peripheral nerves in compression and entrapment neuropathies. However, there is a relative paucity of literature on MRN appearance of diffuse peripheral nerve lesions. We attempted to highlight the salient imaging features of myriad diffuse peripheral nerve disorders and imaging techniques for MRN. Using clinical and pathologically proved relevant examples, we present the MRN appearance of various types of diffuse peripheral nerve lesions, such as traumatic, inflammatory, infectious, hereditary, radiation-induced, neoplastic, and tumor variants.