Neuropsychological and quality of life outcomes 12 months after unilateral thalamic stimulation for essential tremor

OBJECTIVES

To evaluate the one year cognitive, mood state, and quality of life (QoL) outcomes of unilateral thalamic deep brain stimulation (DBS) for essential tremor (ET).

METHODS

40 patients diagnosed with ET completed comprehensive neuropsychological assessments about one month before and three and 12 months after DBS electrode implantation. Data were subjected to multivariate analyses, and significant results were further analysed using univariate techniques.

RESULTS

Analyses revealed statistically significant improvements on a cognitive screening measure and in aspects of fine visuomotor and visuoperceptual functions, verbal memory, mood state, and QoL. No group-wise declines in cognition were observed, but more patients showed declines than improvements on language and visual memory tests. Semantic verbal fluency declined significantly in four (10%) of the patients. In these four patients, diminished lexical verbal fluency was present at baseline.

CONCLUSION

Cognitive, mood, and QoL outcomes after one year of DBS for ET are favourable; there were no overall deleterious effects on cognition, and DBS was accompanied by a significant reduction in anxiety and improvements in quality of life. However, preoperative verbal fluency diminution may predispose to further fluency declines after DBS.

Neuropsychological and quality of life changes following unilateral thalamic deep brain stimulation in Parkinson's disease: a one-year follow-up

BACKGROUND

The long-term neuropsychological and quality of life (QOL) outcomes of unilateral thalamic deep brain stimulation (DBS) in patients with intractable Parkinson's disease (PD) have not heretofore been described.

METHOD

Six patients diagnosed with PD underwent unilateral DBS implantation into a verified thalamic VIM nucleus target. Participants completed presurgical neuropsychological evaluation and follow-up assessment at approximately one year postsurgery.

FINDINGS

Compared to their presurgical scores, PD patients exhibited significant improvement on measures of conceptualization, verbal memory, emotional adjustment, and QOL at one-year follow-up. A few nominal declines were observed across the battery of tests.

INTERPRETATION

These data provide preliminary support for the long-term neurocognitive safety and QOL improvements following thalamic stimulation in patients with PD.

Vagal and sciatic nerve stimulation have complex, time-dependent effects on chemically-induced seizures: a controlled study

Previous studies of the effects of electrical vagus stimulation on experimental seizures were without suitable controls or statistical validation, and ignored the potential role of vagally-induced hemodynamic depression on seizure expression. This study addresses these limitations. The effects of periodic left vagus nerve stimulation (LVNS) on chemically-induced seizures in rats were compared with control groups receiving no stimulation (NoS), left sciatic nerve stimulation (LSNS) and LVNS after pretreatment with methyl atropine (MA-LVNS). Stimulation followed a 30 s on-120 s off cycle over 130 min. Seizures were scored visually and the temporal variation of their probability P(s) across the stimulation cycle was measured statistically. P(s) was significantly different (P<0.01) for all groups: LSNS had the highest and MA-LVNS the lowest seizure probability; LVNS and NoS had intermediate values. While LVNS blocked seizures, it also precipitated them, explaining why its anti-seizure effect was only slightly greater than NoS. Neither LVNS nor MA-LVNS induced changes in cortical rhythms ('activation') associated with decreased P(s), unlike LSNS which increased cortical rhythm synchrony and with it, P(s). LVNS alone induced marked bradycardia and moderate hypoxemia. In conclusion, cranial and peripheral nerve stimulation have complex, time-varying effects on cerebral excitability: low frequency LSNS facilitated seizures, while LVNS both suppressed and facilitated them. The anti-seizure effect of LVNS was small and may have, in part, been due to a hemodynamically-induced deficit in energy substrates. The effects of MA-LVNS on seizure duration and P(s) raise the possibility that, in the absence of hemodynamic depression, stimulation of this nerve does not have a strong anti-seizure effect.

An introduction to contingent (closed-loop) brain electrical stimulation for seizure blockage, to ultra-short-term clinical trials, and to multidimensional statistical analysis of therapeutic efficacy

Automated seizure blockage is a top research priority of the American Epilepsy Society. This delivery modality (referred to herein as contingent or closed loop) requires for implementation a seizure detection algorithm for control of delivery of therapy via a suitable device. The authors address the many potential advantages of this modality over conventional alternatives (periodic or continuous), and the challenges it poses in the design and analysis of trials to assess efficacy and safety-in the particular context of direct delivery of electrical stimulation to brain tissue. The experimental designs of closed-loop therapies are currently limited by ethical, technical, medical, and practical considerations. One type of design that has been used successfully in an in-hospital "closed-loop" trial using subjects undergoing epilepsy surgery evaluation as their own controls is discussed in detail. This design performs a two-way comparison of seizure intensity, duration, and extent of spread between the control (surgery evaluation) versus the experimental phase, and, within the experimental phase, between treated versus untreated seizures. The proposed statistical analysis is based on a linear model that accounts for possible circadian effects, changes in treatment protocols, and other important factors such as change in seizure probability. The analysis is illustrated using seizure intensity as one of several possible end points from one of the subjects who participated in this trial. In-hospital ultra-short-term trials to assess safety and efficacy of closed-loop delivery of electrical stimulation for seizure blockage are both feasible and valuable.

Long term safety and efficacy of unilateral deep brain stimulation of the thalamus for parkinsonian tremor

The objective was to investigate the long term safety and efficacy of unilateral deep brain stimulation (DBS) of the VIM nucleus of the thalamus in Parkinson's disease. Twelve patients with Parkinson's disease underwent unilateral DBS of the thalamus for medication resistant tremor between 1994 and 1997. Patients were evaluated with the motor section of the unified Parkinson's disease rating scale (UPDRS) in the medication on state at baseline, 3 months, 12 months, and yearly thereafter.Three patients were lost to follow up. Nine patients had follow up evaluations greater than 24 months and were included in the analyses. The last postsurgical follow up occurred on average 40.0 (SD 17.2) months after surgery. Tremor scores were significantly improved with stimulation on at the long term follow up compared with baseline. There was no significant change in UPDRS motor scores at long term follow up compared with baseline. There was no significant change in any stimulus parameters from 3 months to the long term follow up. Two patients had asymptomatic intracerebral haemorrhages and one patient had a subcutaneous haematoma over the implantable pulse generator site. Stimulus related adverse reactions were mild and easily controlled with changes in stimulus parameters. Two patients had replacement of the implantable pulse generator due to normal battery depletion, one patient had lead repositioning due to migration, and one patient had the lead extension wire replaced due to erosion. In conclusion, unilateral DBS of the thalamus has long term efficacy for treatment of tremor due to Parkinson's disease.

Spectrum of clinical and histopathologic responses to intracranial electrodes: from multifocal aseptic meningitis to multifocal hypersensitivity-type meningovasculitis

PURPOSE

We sought to characterize and compare the histopathologic and clinical changes elicited by subdural and depth electrodes in subjects undergoing epilepsy surgery evaluation.

METHODS

A retrospective review of clinical records, imaging and histopathologic studies of epilepsy surgery cases requiring subdural strips and depth electrodes for localization of epileptogenic tissue was performed between 1993 and 1999. Forty-nine subjects had a combination of subdural and depth, whereas 10 had depth electrodes only. Histopathologic changes were classified as mild, moderate, or severe based on the density, extent, and composition of the inflammatory infiltrate.

RESULTS

Subdural electrodes induced a clinical picture of transient aseptic meningitis; histopathologically, the infiltrates were moderate in degree in the majority (73%) and severe in the remainder (27%), with T cells and eosinophils infiltrating the cortex and arteriolar walls (hypersensitivity-type response). Depth electrodes alone caused minimal or no symptoms of meningeal irritation; the cellular response elicited by these electrodes was mild in five and moderate in the remaining five cases; severe inflammation was not observed in this group. Although the proportion of small clinically silent hematomas was larger in cases with depth (five of 59) compared with subdural electrodes (one of 49), microhemorrhages were considerably more numerous with subdural than with depth electrodes.

CONCLUSIONS

These results suggest that the spectrum of brain responses to foreign bodies is wide, ranging from self-limited physiologic to hypersensitivity-type reactions of varying severity. Subdural strips elicited more intense inflammation than did depth electrodes. The histopathologic extent of the reaction to either type of electrodes could not be precisely defined because of the retrospective nature of this study. History of allergy to latex or previous craniotomies are probable risk factors for the hypersensitivity-type reaction. Surgical outcome, excellent in the majority, was independent of the severity or type of inflammation, and there have not been neurologic or systemic sequelae.

Long-term safety and efficacy of unilateral deep brain stimulation of the thalamus in essential tremor

Our objective was to investigate the long-term safety and efficacy of unilateral deep brain stimulation (DBS) of the VIM nucleus of the thalamus in essential tremor. Forty-nine patients were evaluated for DBS between December 1993 and March 1998. Tremor was assessed by a clinical rating scale at 3 and 12 months and then yearly. Three patients were not implanted, seven were explanted prior to 24 months, 11 were lost to long-term follow-up, and three died from unrelated causes. Twenty-five patients were evaluated with follow-up greater than or equal to 2 years. The last postsurgical follow-up occurred on average 40.2 +/- 14.7 months after surgery. Tremor scores were significantly improved with stimulation on at the long-term follow-up as compared to baseline. There was no change in tremor scores from baseline to long-term follow-up with stimulation off. There was no significant change in any stimulus parameters from 3 months to the long-term follow-up. Three patients had asymptomatic intracerebral hemorrhages and one patient had postoperative seizures. Stimulus-related adverse reactions were mild and easily controlled with changes in stimulus parameters. Device-related complications were common and required repeated surgical procedures. Unilateral DBS of the thalamus has long-term efficacy in some patients for treatment of essential tremor. However, this therapy is compromised by loss of efficacy in some patients and device complications which increase the risk of additional surgical procedures.

Deep brain stimulation of the Vim nucleus of the thalamus for the treatment of tremor

The surgical treatment of tremor has evolved considerably in the past few years. Of the several conditions associated with severe tremor, the most common are Parkinson's disease (PD) and essential tremor (ET). Levodopa therapy reduced drastically the number of patients with PD who require surgery because of inadequate control. However, there remains a small number of "tremor dominant" PD patients for whom surgical treatment is often the best option. The ventralis intermediate nucleus (Vim) of the thalamus has been the preferred surgical target for the treatment of parkinsonian tremor for many years, but this is now challenged by the subthalamic nucleus (STN). Deep brain stimulation (DBS) of either target possesses high therapeutic efficacy against tremor in PD. ET may be difficult to treat pharmacologically. Thalamotomy is an effective surgical procedure for ameliorating ET but may be associated with persistent neurologic deficits. DBS of the thalamus is also a highly effective means of reducing ET. DBS appears to be safer than thalamotomy and is now the recommended surgical procedure.

Comparison of thalamotomy to deep brain stimulation of the thalamus in essential tremor

OBJECTIVE

To compare outcome in Essential Tremor (ET) patients who have undergone either thalamotomy or Deep Brain Stimulation (DBS) of the thalamus.

BACKGROUND

Although both thalamotomy and thalamic DBS are effective surgical treatments of tremor, it is not known if one procedure is superior to the other.

DESIGN/METHODS

Thirty-five ET patients underwent thalamotomy between 1994-1998. Data on 18 patients were excluded. The remaining 17 patients were matched for age, sex, side of surgery, and tremor severity to 17 ET patients who underwent thalamic DBS. There were nine men and eight women in each group. The mean age of the thalamotomy group was 74.4 years and that of the thalamic DBS group was 73.1 years.

RESULTS

There were no significant differences between any efficacy outcome variables comparing thalamotomy to DBS of the thalamus at baseline or follow-up visits. The surgical complications were higher for the thalamotomy group as compared to the DBS group. However, a larger number of DBS patients underwent repeat surgeries due to problems with the device and the leads.

CONCLUSION

Although the efficacy is similar for thalamotomy and DBS of the thalamus for ET, thalamotomy is associated with a higher complication rate. DBS of the thalamus should be the procedure of choice for the surgical treatment of ET in most cases.

Effect and time course of deep brain stimulation of the globus pallidus and subthalamus on motor features of Parkinson's disease

We studied the effect and temporal profile of deep brain stimulation (DBS) of the globus pallidus and subthalamic nucleus on the motor signs of Parkinson's disease (PD). Four patients with bilateral deep brain stimulators of the globus pallidus and four patients with bilateral deep brain stimulators of the subthalamus were studied while taking no medication and at 15 and 30 minutes and 1, 2, 4, and 6 hours after turning stimulation on. An immediate (15 minutes) and sustained (6 hours) benefit was observed for all the motor manifestations of PD for both stimulation sites. Deep brain stimulation of the globus pallidus and subthalamus is highly effective in reducing all the cardinal motor features of PD.

Health-related quality of life in Parkinson's disease after pallidotomy and deep brain stimulation

This study explored the multidimensional outcome of three neurosurgical interventions for Parkinson's disease (PD): pallidotomy (N = 23), pallidal deep brain stimulation (DBS) (N = 9), and thalamic DBS (N = 7). All patients completed the Sickness Impact Profile (SIP) and the Beck Depression Inventory. Pallidotomy patients also completed the Profile of Mood States, the Beck Anxiety Inventory, and a disease-specific quality of life (QOL) measure, the Parkinson's Disease Questionnaire (PDQ-39). Three months after surgery, all neurosurgical groups showed significant improvements in mood and function, including physical, psychosocial, and overall functioning. Pallidal DBS and pallidotomy patients who completed additional QOL measures reported decreased anxiety and tension, increased vigor, improved mobility and ability to perform activities of daily living, and decreased perceived stigma. Psychosocial dysfunction scores from the SIP were related to depressed mood both at baseline (r = .42) and at followup (r = .45), but the physical dysfunction subscale was not related to mood at either time point, suggesting that disruption of social relationships due to PD may have more impact on affective distress than physical symptoms alone. Results suggest that neurosurgical interventions for PD improve disabling PD motor symptoms and also improve several domains of quality of life.

Neuropsychological and quality of life outcome after thalamic stimulation for essential tremor

OBJECTIVE

To evaluate short-term effects of unilateral thalamic deep brain stimulation (DBS) on cognition, mood state, and quality of life in patients with essential tremor (ET).

BACKGROUND

Unilateral thalamotomy and thalamic DBS are effective in alleviating refractory tremor contralateral to the side of surgery. Thalamotomy can lead to cognitive morbidity, and DBS might be a preferable surgical intervention given potential avoidance or reversibility of such morbidity. Although unilateral thalamic DBS is cognitively safe and leads to quality of life improvement in PD, its neurobehavioral effects in ET are unknown.

METHODS

Forty patients with ET were administered a broad neuropsychological test battery, measures of mood state, and generic and disease-specific quality of life measures approximately 1 month before and 3 months after surgery (left hemisphere, 38 patients).

RESULTS

Unilateral thalamic DBS was associated with significant improvements in tremor and dominant-hand fine visuomotor coordination. Statistically significant but clinically modest gains were observed on tasks of visuoperceptual and constructional ability, visual attention, delayed word list recognition, and prose recall. Only lexical verbal fluency declined significantly after surgery. Patients rated themselves as less anxious after surgery, and they perceived their quality of life as improved significantly. In particular, patients reported improved quality of life with respect to activities of daily living, stigma, emotional well-being, and communication.

CONCLUSIONS

Unilateral thalamic DBS for ET is cognitively safe and associated with improvements in anxiety and quality of life in the near term and in the absence of operative complications. Patients were better able to carry out activities of daily living after surgery, and they reported improvement in several psychosocial domains of quality of life.

Bilateral thalamic stimulation for the treatment of essential tremor

OBJECTIVE

To determine the safety and efficacy of bilateral thalamic stimulation in the treatment of essential tremor (ET).

METHODS

Nine ET patients with disabling tremor refractory to pharmacotherapy underwent bilateral staged implants. Tremor was assessed by the Fahn-Tolosa-Marin Tremor Rating Scale at baseline 1 (before first implant), baseline 2 (before second implant), and at 6-month and 1-year follow-up. Blinded evaluations were performed at 3 months. Associated changes in speech were evaluated in six patients. There were seven men and two women with a mean age of 73.8 years.

RESULTS

There was a significant improvement in the mean total tremor score from a baseline of 66.1+/-11.6 to 28.4+/-12.8 12 months after the second surgery. Similarly, the mean motor tremor subscore was 20.1+/-5.0 before the first surgery and improved significantly to 14.1+/-3.6 before the second surgery. Motor tremor scores 6 months after the second surgery (6.0+/-3.7) and 12 months after the second surgery (7.5+/-3.9) also improved significantly relative to the preoperative scores. The mean activities of daily living (ADL) subscore at baseline was 18.2+/-2.9 and improved significantly before the second surgery to 9.0+/-3.2. These ADL scores further improved 6 months (6.2+/-5.2) and 12 months (7.9+/-5.7) following the second surgery, but these gains were not significant. Blinded evaluations also revealed a similar degree of improvement. Complications were noted in five patients: asymptomatic intracranial hematoma (1), postoperative seizures (1), a hematoma over the implanted pulse generator (IPG) (1), lead repositioning (1), and IPG malfunction (1). Adverse effects related to stimulation were mild and resolved with adjustment of the stimulation parameters. Three of the six patients demonstrated worsening of dysarthria with both stimulators on.

CONCLUSIONS

Bilateral thalamic stimulation is effective in reducing tremor and functional disability in ET; however, dysarthria is a possible complication.

Cognitive outcome following staged bilateral pallidal stimulation for the treatment of Parkinson's disease

As neurosurgical treatment of parkinsonian symptoms has become increasingly popular, concern about the cognitive morbidity which may result from such interventions has risen proportionately. Previous reports of cognitive difficulties associated with pallidotomy and thalamotomy, especially in bilateral cases, have provided the impetus for research into chronic electrical deep brain stimulation procedures which are believed to be safer than ablation. Given the lack of neurobehavioral research following bilateral deep brain stimulation procedures, this preliminary study of six Parkinson's disease patients undergoing staged bilateral pallidal stimulation was undertaken. A battery of tests assessing attention, executive function, visuomotor coordination, language, visuoperceptual function, learning memory and mood revealed no significant change in overall level of cognitive functioning after either unilateral or bilateral pallidal deep brain stimulation. No significant declines were observed about three months following bilateral stimulation, and in fact, significant gains in delayed recall and relief of anxiety symptoms were noted. It was concluded from this preliminary data that bilateral pallidal stimulation for the treatment of Parkinson's disease, at least in the absence of operative complications, offers a cognitively safe alternative to ablation.

Efficacy of unilateral deep brain stimulation of the VIM nucleus of the thalamus for essential head tremor

Essential tremor is a common movement disorder. Deep brain stimulation of the VIM nucleus of the thalamus has been reported to be efficacious for reducing essential hand tremor. The effect of deep brain stimulation of the thalamus on essential head tremor has not been well studied. Therefore, we evaluated the effect of DBS of the thalamus in 38 patients with essential head tremor. Head tremor scores prior to surgery were compared with scores at 3, 6, and 12 months postimplant with stimulation "on" and "off." The 3-month evaluations were blinded for 24 patients and all others were open-label. There was a significant improvement in head tremor at all postimplant evaluations compared with baseline. Essential head tremor can be reduced with deep brain stimulation of the VIM nucleus of the thalamus and, pending the results of other controlled trials, should be considered as a treatment option for patients with disabling essential head tremor unresponsive to medication.

Chronic electrical stimulation of the left ventrointermediate (Vim) thalamic nucleus for the treatment of pharmacotherapy-resistant Parkinson's disease: a differential impact on access to semantic and episodic memory?

Thalamotomy for medically refractory Parkinson's disease (PD) is considered to be efficacious and relatively safe. Because a minority of patients experience decrements in language and memory (often mild and transient) after thalamotomy, chronic thalamic deep brain stimulation (DBS) might be a safer treatment given its reversibility and the modifiability of stimulation parameters. Two preliminary studies support the relative cognitive safety of unilateral DBS of the ventral intermediate (Vim) thalamic nucleus, but it is unclear whether possibly subtle changes in language and memory represent effects of "microthalamotomy" or of stimulation per se. This report provides preliminary data concerning effects of left thalamic stimulation on information processing speed, semantic memory (verbal fluency and visual confrontation naming), and verbal episodic memory in a patient with PD. In addition to being evaluated before and 3 and 6 months after surgery, the patient was tested 18 months after surgery either on or off medications and with the stimulator turned either on or off (order counterbalanced across medication conditions). Test performance differences between the stimulation conditions were attenuated "off" as compared to "on" medication. Vim stimulation consistently, albeit subtly, improved semantic verbal fluency but interfered with immediate recall of word lists. Parallels to findings from acute, intraoperative thalamic stimulation studies are explored. The hypothesis is offered that left Vim stimulation might facilitate access to semantic memory, but interfere with episodic memory processes.

Real-time automated detection and quantitative analysis of seizures and short-term prediction of clinical onset

PURPOSE

We describe an algorithm for rapid real-time detection, quantitation, localization of seizures, and prediction of their clinical onset.

METHODS

Advanced digital signal processing techniques used in time-frequency localization, image processing, and identification of time-varying stochastic systems were used to develop the algorithm, which operates in generic or adaptable "modes." The "generic mode" was tested on (a) 125 partial seizures (each contained in a 10-min segment) involving the mesial temporal regions and recorded using depth electrodes from 16 subjects, and (b) 205 ten-minute segments of randomly selected interictal (nonseizure) data. The performance of the algorithm was compared with expert visual analysis, the current "gold standard."

RESULTS

The generic algorithm achieved perfect sensitivity and specificity (no false-positive and no false-negative detections) over the entire data set. Seizure intensity, a novel measure that seems clinically relevant, ranged between 35.7 and 6129. Detection was sufficiently rapid to allow prediction of clinical onset in 92% of seizures by a mean of 15.5 s.

CONCLUSIONS

This algorithm, which was implemented with a personal computer, represents a definitive step toward rapid and accurate detection and prediction of seizures. It may also enable development of intelligent devices for automated seizure warning and treatment and stimulate new study of the dynamics of seizures and of the epileptic brain.

Reduction in voice tremor under thalamic stimulation

We studied the effect of deep brain stimulation (DBS) of the ventral intermediate thalamic nucleus on voice symptoms in seven patients with essential tremor. All had undergone DBS for management of hand tremor. Five of the patients had received unilateral implants; two were treated bilaterally. Each reported improvement in hand tremor with thalamic stimulation (a 1-to-3-point change on a 5-point severity scale). Voice tremor was evaluated with and without stimulation using patient and clinician severity ratings, and acoustic measures (rate and amplitude). Four of the seven patients showed reductions in voice symptoms in at least two of these measures, although degree of change differed (e.g., from 1 to 3 points on the 5-point severity scale). Voice gains typically were restricted to those patients with the more severe symptoms and did not parallel improvements in the upper extremities. It appears that reduced voice tremor may be an additional benefit of DBS for some individuals.

Rhabdoid transformation of tumor cells in meningiomas: a histologic indication of increased proliferative activity: report of four cases

Four cases of meningeal tumors in adults (ages ranging from 28 to 84 years) are presented. All had the typical gross appearance of meningiomas at operation. In three tumors, areas of meningothelial or fibroblastic meningiomas showed transition to cell groups of the rhabdoid type. In the fourth case only rhabdoid cells were encountered, possibly representing a total "take-over" of a meningioma by rhabdoid elements. In the three cases with mixed pattern, the rhabdoid cells showed more anaplasia and atypism than the conventional meningiomatous elements. In case 3 this was expressed by very high MIB-1 positivity in the rhabdoid cells and absence of same in the fibroblastic meningiomatous elements. These cases (the first three with certainty, the fourth with a strong likelihood) indicate that the phenotypic changes to cells with "rhabdoid" morphology may involve meningiomas and that such change is associated with aggressive biologic and clinical behavior of the tumors showing this type of alteration.

Unilateral pallidal stimulation for Parkinson's disease: neurobehavioral functioning before and 3 months after electrode implantation

Unilateral pallidotomy is thought to have a low risk for cognitive morbidity. Nonetheless, recent research suggests that some patients experience declines in memory and language and that pallidal stimulation might be a safer treatment for Parkinson's disease (PD). We investigated the neurobehavioral effects of unilateral pallidal stimulation. Nine consecutive PD patients undergoing unilateral deep brain-stimulating electrode implantation in the globus pallidus interna were evaluated with a neuropsychological test battery approximately 1 month before and 3 months after surgery. Patients reported significantly fewer symptoms of anxiety and greater vigor after surgery. There was a trend toward fewer depressive symptoms. Semantic verbal fluency and visuoconstructional test scores declined significantly after surgery. However, among five patients showing declines in semantic verbal fluency, only one patient's score declined by more than 2 SD. No patient showed significant decline or improvement in the overall level of cognitive functioning. This study supports the relative safety, in terms of cognitive function, of unilateral pallidal stimulation in PD.

Three-dimensional computerized reconstruction. Illustration of incremental articular cartilage thinning

RATIONALE AND OBJECTIVES

The authors have addressed the ability of magnetic resonance (MR) imaging to resolve incremental thinning of articular cartilage by assessment of three-dimensional (3-D) and two-dimensional (2-D) representations.

METHODS

Using a porcine knee model, sequential cartilage shavings were characterized using a 3-D fat suppressed spoiled gradient-echo (SPGR) MR imaging protocol that provided good contrast between high-signal articular cartilage and lower signal surrounding tissues. Lesion dimensional measurements were made on both MR images and 3-D computerized reconstructions. Volumes of cartilage removed were approximately 0.06 mL.

RESULTS

Incremental articular cartilage thinning typically was apparent on 3-D reconstructed images. Three-dimensional articular cartilage reconstructions were effective in depicting location and orientation of shaved cartilage regions. Average percent error associated with length and with measurements based on 2-D MR images was approximately 19% for observer 1 and 33% for observer 2 when compared with direct measurements of the shaved cartilage. Average percent error of thickness measurements based on 2-D MR was approximately 21% for observer 1 and 37% for observer 2. Overall average errors associated with length, width, and thickness measurements were approximately 25%.

CONCLUSIONS

Incremental thinning of articular cartilage can be tracked qualitatively and quantitatively using 3-D computerized reconstructions and 2-D MR images. Errors associated with the quantitative measurements can be attributed to limitations of measurement methods and intrinsic limitation of MR resolution.

Textural parameters based on the Spatial Gray Level Dependence Method applied to melanocytic nevi

The purpose of this study is to evaluate the Spatial Gray Level Dependence Method (SGLDM) of texture analysis with respect to its ability to discriminate between melanocytic nevi and normal skin. Thirteen textural features based on the SGLDM were evaluated with respect to their relative sensitivities to both texture and tone. Ten features were found to be more sensitive to texture than tone and were selected for further study. Twenty-four digitized images of benign melanocytic nevi were obtained from six volunteers. Ten textural features were analyzed for each nevus and for surrounding sections of normal skin. Of these 10 features, 8 features can distinguish between textural properties of melanocytic nevi and surrounding skin.

Analysis of three-dimensional computerized representations of articular cartilage lesions

RATIONALE AND OBJECTIVES

The authors assess the accuracy of three-dimensional (3D) computer representations based on magnetic resonance images of articular cartilage lesions, using actual cartilage lesions as reference standards.

METHODS

Grade 2 and grade 3 articular lesions were created on articular surfaces of five porcine knee joints. The knees were then imaged using 3D fat-suppressed SPGR acquisition at four different slice thicknesses. Magnetic resonance imaging data sets were transferred to a computer workstation for image processing and 3D reconstruction. Lesion dimensions (length, width, and depth) based on the 3D reconstructed image were compared with the dimensions measured using actual lesions.

RESULTS

The average percent error of lesion length, width, and depth based on the 3D images ranged from approximately 8% to 12% when using the thinnest magnetic resonance slice thickness (0.7 mm).

CONCLUSIONS

Three-dimensional reconstructed images derived from thin-slice magnetic resonance imaging can provide reasonable representations of true articular cartilage lesion dimensions.

Synovial cysts of the lumbar spine: diagnosis, surgical management, and pathogenesis. Report of eight cases

BACKGROUND

Synovial cysts are uncommon extradural degenerative lesions associated with symptoms of lower back pain and radiculopathy. Most of these lesions occur in the lumbar spine at the L4-5 level and to a lesser extent at the L5-S1 and L3-4 levels.

METHODS

A retrospective study involving eight patients seen by the neurosurgery service from January 1, 1989, to May 30, 1994, was analyzed. The type, duration, and distribution of symptoms were evaluated, along with the patient's age and sex. All patients had lumbosacral spine x rays and magnetic resonance imaging. Four had a computed tomography-myelogram of the lumbar spine. All patients underwent a laminectomy or hemilaminectomy and cyst excision, and all were followed for a minimum of 1 year. The presence of a synovial cyst was confirmed by histopathology.

RESULTS

Of the eight patients, seven had dramatic pain relief with five having complete resolution of pain. The single care of persistent pain was found to be due to scar tissue at the operative site. All five cases of preoperative lower extremity weakness showed complete resolution. Dysesthesia was either unchanged or decreased.

CONCLUSIONS

Surgery is a safe, effective treatment for patients with lumbar synovial cysts and is the treatment of choice for these lesions.

Magnetic resonance imaging and pathological analysis of a pituicytoma: case report

A case of a pituicytoma is presented that describes the clinical, pathological, and magnetic resonance imaging features of a rare tumor of the neurohypophysis. A 26-year-old woman presented with a 4-month history of dizziness and visual obscuration. A magnetic resonance image revealed a pituitary mass with suprasellar extension. The specimen obtained from a transsphenoidal decompression identified the mass as an astrocytoma of the posterior pituitary (pituicytoma). Immunohistochemical staining was positive for glial fibrillary acidic protein, S-100, and vimentin. Electron microscopy identified intermediate filaments, numerous broad cell junctions, no secretory granules, and two cellular populations with either an electron-dense or lucent cytoplasmic matrix. This case is unique in that other documented cases originating in the posterior pituitary have all been pilocytic astrocytomas, whereas this neoplasm was not a pilocytic variant. This is also the first case in the literature of a pituicytoma documented by magnetic resonance imaging. This report reviews the cytological elements of the neurohypophysis and the origin of pituicytomas and stresses the proper use of the term "pituicytoma" in relation to tumors of the posterior pituitary.

Hematoma in the posterior fossa secondary to a tangential gunshot wound of the occiput: case report and discussion

The case of 16-year-old boy who incurred a subdural hematoma in the posterior fossa an intracerebellar hematoma after a tangential civilian gunshot wound is reported. The skull was not fractured, and yet surgically significant clots required removal. The patient recovered. The discussion centers on the mechanism of injury and seriousness of tangential gunshot wounds and traumatic hematomas in the posterior fossa.