D L Daniels

Can We Distinguish Between Benign Versus Malignant Compression Fractures of the Spine by Magnetic Resonance Imaging

Study Design The authors investigate the usefulness of magnetic resonance imaging in differentiating benign versus malignan compression fractures by reviewing patients and a fracture model in a canine model. Objectives To determine the sensitivity and specificity of magnetic resonance imaging in differentiating benign versus malignant compression fractures of the spine and to obtain distinguishing features in magnetic resonance imaging. Summary of Background Data The differentiation between benign and abnormal compression fractures of the thoracolumbar spine has important implications regarding patient treatment and prognosis. Plain radiographs, bone scans, and computed tomography are not accurate imaging modalities for this purpose. Methods Magnetic resonance imaging scans of 22 patients with confirmed lesions of the thoracolumbar spine were studied. There were 11 malignant and 11 benign lesions. Two experienced neuroadiologists blindly reviewed the magnetic resonance imaging scans and determined benign or malignant lesions. A canine study was performed to simulate a compression fracture model with a vertebral osteotomy in two dogs, and serial contrast-enhanced magnetic resonance imaging scans were performed 15, 30, 60 and 90 days after surgery. Results The correct interpretation between two neuroradiologists was 77% and 95%. The combined sensitivity rate was 88.5%, and the specificity rate was 89.5%. Magnetic resonance imaging reliably distinguished beningn versus malignant lesions based on the anatomic distribution and intensity of signal changes of bone and adjacent tissues, contrast enhancement characteristics, and changes over time. Only one malignant lesion was misinterpreted by both neuroradiologists as benign, whereas there was one additional missed malignant lesion and three misinterpreted benign lesions by one radiologist. In the canine study, signal changes and enhancement were found 60 days after surgery, but no signal changes or enhancement were noted on the scan 90 days after surgery. Conclusions Magnetic resonance imaging scans can detect malignant vertebral lesions early, but acute healing compression fractures may mimic the findings of metastatic lesions. The use of contrast-enhanced magnetic resonance imaging scans and serial magnetic resonance imagings are helpful for additional differentiation between benign and malignant compression fractures. In addition to magnetic resonance imaging scans, other diagnostic tests and clinical findings should be correlated before biopsy or surgery of the suspected lesion.

Cortical activation response to acoustic echo planar scanner noise.

PURPOSE Our goal was to determine the distribution of auditory and language cortex activation in response to acoustic echo planar scanner noise with functional MRI (fMRI). METHOD Acoustic scanner noise and spoken text, reproduced on high output cassette tape, were separately delivered at equivalent intensities to six normal hearing adult volunteers through earphones during fMRI data acquisition. In nine other subjects, taped scanner noise was delivered in five successive iterations of the task to assess the consistency of cortical activation to the noise stimulus. Gyri of the auditory and language system were divided into 10 different subregions for analysis of cortical activation. The number of activated pixels and proportion of volunteers activating each cortical subregion were determined using a cross-correlation analysis. RESULTS Cortical activation to taped acoustic scanner noise was present within the transverse temporal gyrus (primary auditory cortex) in all subjects, but activation was highly variable between subjects in auditory association and language relevant cortex. Auditory association cortex activation was seen in the planum polari, planum temporali, and middle temporal gyrus/superior temporal sulcus regions in one-half to two-thirds of the volunteers. There was no significant difference in the distribution of cortical activation within individual subjects across five successive iterations of the scanner noise task. Listening to spoken text consistently activated primary and association auditory cortex bilaterally as well as language relevant cortex in some cases. The mean number of activated pixels was significantly greater for text listening than acoustic scanner noise in auditory association and language relevant cortical subregions (p < 0.01), although the distribution of activity was similar between the two tasks. CONCLUSION This preliminary investigation suggests that the complex sounds produced by the echo planar pulse sequence can activate relatively large regions of auditory and language cortex bilaterally, with the extent of activation outside the primary auditory cortex being variable between subjects. However, the distribution of activation within individual subjects was relatively constant across several iterations of the scanner noise stimulus.

Gadolinium-enhanced magnetic resonance imaging in facial nerve lesions.

We present our 2-year experience with a contrast enhancement agent in magnetic resonance imaging (MRI) examining facial nerve pathology. Characteristics of the agent gadolinium diethylenetriamine pentaacetic acid are reviewed. The radiographic capability to differentiate pathologic vs. normal facial nerves based on enhancement and a change in signal intensity generated by the nerve is demonstrated. Experience with facial nerve disorders including Bells palsy, facial nerve neuromas, a facial nerve graft site, postoperative facial paralysis, and traumatic facial paralysis is presented. The ability to image the facial nerve in Bells palsy provides an entirely new means of examining this disorder, and its implications are discussed. The ability to enhance the paralyzed facial nerve in the temporal bone after posterior fossa surgery supports a previously held concept as to the pathophysiology of this problem.

Intensity-dependent activation of the primary auditory cortex in functional magnetic resonance imaging.

Purpose The purpose of this study was to investigate the activation patterns of the primary auditory cortex in response to varying intensities of pure tone stimuli. Method A 1,000-Hz pure tone stimulus was delivered monaurally to the right ear of 12 normal-hearing right-handed volunteers in 20-second on-off cycles. Stimuli were applied at 20 and 50 dB hearing level (HL) above threshold in 12 subjects and at 0, 20, 40, and 50 dB HL above threshold in 6 subjects. Functional magnetic resonance imaging (fMRI) data were obtained using a 1.5-T scanner and echoplanar imaging. Activated pixels were identified in the transverse temporal gyrus (TTG) of both hemispheres in response to pure tone stimuli at each intensity level using cross-correlation analysis (0.6;P < 0.0001). Results Of the 24 right and left TTGs imaged (n = 12), activation to pure tone stimuli at 20 and 50 dB HL above threshold was seen in 46% and 79% of TTGs, respectively, with bilateral hemispheric activation in 27% and 64% of subjects, respectively. The mean numbers of activated voxels were 4.0 and 13.0, respectively. Of the 12 right and left TTGs imaged at 0, 20, 40, and 50 dB HL above threshold, activation was seen in 33%, 42%, 58%, and 75% of TTGs, respectively. The mean numbers of activated voxels were 5.8, 3.2, 9.8, and 15.3, respectively. There was a nonsignificant trend toward contralateral (left) dominant TTG activation with increased tone intensity. Conclusion Our results show an increased likelihood of TTG activation, increased TTG activation volume, and increased bilateral hemisphere TTG activation with increasing pure tone intensity. Our results suggest that the primary auditory cortex reflects or is directly involved in the central processing of sound intensity and that varying the intensity of even simple stimuli can alter the patterns of fMRI activation in auditory cortex.

The use of gadolinium‐enhanced magnetic resonance imaging to determine lesion site in traumatic facial paralysis

Gadolinium‐enhanced magnetic resonance imaging has been used to evaluate 20 patients with surgically confirmed facial nerve lesions. When the nerve could be seen, gadolinium‐enhanced magnetic resonance imaging accurately revealed the lesion site as well as the known extent, which in some cases was not predicted by topognostic testing. This technique appears to provide accurate lesion‐site testing and may have importance in surgical planning. Currently used topognostic tests of facial nerve function are frequently inaccurate and can only determine the most proximal lesion site when there are multiple or extensive lesions.

Gradient recalled echo MR imaging of superior sagittal sinus occlusion

SummaryWith T1-weighted gradient recalled echo (GRE) MR images and flow compensation, we studied the superior sagittal sinus in 3 normal volunteers and 3 patients with sinus occlusion. In these images, sites of patency of the superior sagittal sinus were identified due to the high signal intensity of the normal sinus. Tumor invading the sinus was nearly isointense with cerebral gray matter. T1-weighted GRE imaging proves to be an effective technique to evaluate sinus blood flow.

Gas in spinal articulations

SummaryThe purpose of this review is to illustrate, some for the first time, a variety of gas collections in lumbar facet joints and intervertebral discs and in the sacroiliac joint.

The effect of intracranial surgical trauma on gadolinium-enhanced magnetic resonance imaging

Gadolinium‐enhanced magnetic resonance imaging (MRI) is currently the gold standard for diagnosis of an acoustic neuroma. Its status in diagnosis of a recurrent or residual neuroma is not nearly as clear. A pilot study of 36 postoperative cases showed enhancement in 100% of the patients at the operative site. To examine the role of surgical trauma and biodegradable packing on enhanced MRI, an animal study was designed. Cats and monkeys that underwent posterior fossa surgical procedures had preoperative and postoperative MRI and histologic correlation of any enhanced area. Areas of postoperative enhancement should not be considered as diagnostic of tumor. Further studies are necessary to develop a criteria for recurrent tumor diagnosis with enhanced MRI.

Arteriovenous Malformation Simulating a Cyst on Computed Tomography

Three cases are described in which an intracerebral arteriovenous malformation (AVM) was accompanied by a cystic component probably resulting from hemorrhage. The 3 patients gave a history of headaches. In cases of low-attenuating nonenhancing CT processes, an AVM must be considered.

Surface Coil MR Evaluation of a Lacrimal Gland Carcinoma

Recognition of both bone involvement and extraorbital spread of tumor is essential for the correct diagnosis and treatment of lacrimal fossa masses. We present a case of adenoid cystic carcinoma of the lacrimal gland where bone invasion and extraorbital extension were better defined with magnetic resonance imaging than with CT.