Two cases of unexpected long-term improvement of Parkinson's disease after subthalamic nucleus deep brain stimulation removal.

Two patients with Parkinson's disease (PD) treated successfully with subthalamic nucleus deep brain stimulation (STN-DBS) for 3-4 years are reported, who demonstrated a persistent improvement following removal of STN-DBS for late infection. Possible hypotheses are discussed--whether a microlesioning effect or a disease-modifying effect of STN-DBS, though neither adequately explain this phenomenon.

Deep brain stimulation in dystonia: State of art and future directions.

When considering Deep Brain Stimulation (DBS) surgical treatment of dystonia syndromes, it is important to consider multiple aspects of the disease and its presentation. It is crucial to know if the dystonia is idiopathic, inherited or acquired as well as focal, segmental or generalised. Careful phenotyping of idiopathic as well as inherited dystonias and accurate diagnosis of acquired dystonias informs the decision-making process for patients and clinicians by providing them with useful predictors of outcomes of the proposed surgery. Here, we provided a review of the current literature, highlighted the areas where evidence is scarce and suggested future directions for research.

Primary Nocardia farcinica brain abscess with secondary meningitis and ventriculitis in an immunocompetent patient, successfully treated with moxifloxacin.

We report a rare case of Nocardia farcinica occipital brain abscess in an immunocompetent patient with no underlying risk factors successfully treated with the antibiotic moxifloxacin. The patient underwent craniotomy and abscess drainage. Initial post-operative treatment with co-trimoxazole produced a limited response. Despite the development of skull base meningitis and ventriculitis subsequent addition of moxifloxacin produced an excellent outcome.

In vitro assessment of bacterial adhesion to Hydromer-coated cerebrospinal fluid shunts.

The adherence of five strains of Staphylococcus epidermidis and one strain of S. aureus to both untreated and Hydromer-coated silicone rubber cerebrospinal fluid shunts was studied in vitro using epifluorescent image analysis. All five strains of S. epidermidis showed similar levels of adherence to untreated shunts, whilst S. aureus adhered slightly better. The Hydromer coating, a hydrogel material which creates a hydrophilic layer on the shunt surface, was found to reduce bacterial adhesion levels by approximately 90% in the six strains of bacteria tested. Unfortunately, uniform coverage of the shunt surfaces (particularly internally) with Hydromer coating was not achieved during sample preparation. Bacterial adhesion levels in such areas were identical to untreated controls. This may pose problems in the in vivo use of Hydromer-coated shunts.

Primary intradural classic chondrosarcoma: case report and literature review.

OBJECTIVE AND IMPORTANCE: The exact origin of rare intradural chondrosarcomas remains obscure. We present a case report of an intradural classic chondrosarcoma (a very rare subtype of chondrosarcoma in this location), with a review of the literature, in an attempt to clarify the histogenesis of these tumors. CLINICAL PRESENTATION: A 48-year-old man presented with a 12-month history of progressive right hemiparesis. Computed tomography and magnetic resonance imaging demonstrated a left parietal space-occupying lesion. INTERVENTION: The patient underwent an image-guided, left parietal parasagittal craniotomy. An extrinsic tumor, which seemed to arise from the dura, was macroscopically removed. There was no bone involvement. The histological examination revealed a Grade II classic chondrosarcoma with tumor infiltration into the dura. Adjuvant radiotherapy was administered. CONCLUSION: Intradural chondrosarcomas are rare tumors, the majority of which are mesenchymal. Classic chondrosarcomas in this location are much rarer. Their histogenesis is uncertain. In this case, the origin seems to be from the dura. Because of the malignant potential of these tumors, radical extirpation whenever possible, followed by radiotherapy, is indicated.

Trigeminal neuralgia: a quantitative sensory perception threshold study in patients who had not undergone previous invasive procedures.

The authors investigated 28 patients with "idiopathic" trigeminal neuralgia who had undergone no previous invasive procedures; together these patients had a total of 50 affected trigeminal divisions. Quantitative sensory perception thresholds were measured before operation. Preoperative measurements in the affected divisions indicated raised thresholds for touch (von Frey filaments) and temperature, but not for pinprick or heat pain, in agreement with the findings of Nurmikko. Only the tactile threshold was also significantly affected in the unaffected divisions on the affected side. The authors discuss their findings in relation to the pathophysiology of trigeminal neuralgia, concluding that the origin of the condition is almost certainly central to the gasserian ganglion.

Sensory effects of microvascular decompression in trigeminal neuralgia.

Nineteen patients with "idiopathic" trigeminal neuralgia, who had not undergone any previous interventional procedures, possessed a vessel or vessels compressing the preganglionic nerve root that was demonstrated by magnetic resonance tomographic angiography. Pain was relieved immediately in all of these patients after they underwent microvascular decompression without observed nerve damage. Although preoperative measurement of sensory perception thresholds showed elevations in the thresholds for touch (von Frey filaments) and warmth and coolness sensations, these thresholds normalized during the postoperative period. An apparent deficit in the pinprick (sharpness) sensation appeared postoperatively, but the deficit gradually regressed and completely disappeared by 1 year after surgery; this phenomenon may have been a statistical anomaly. The patients' pain disappeared immediately postoperatively and remained absent throughout the follow-up period. The authors conclude that damage to the nerve or nerve root is not essential for the relief of trigeminal neuralgia.

Somatosensory evoked potentials in intracranial hypertension: analysis of the effects of hypoxia.

The loss of somatosensory evoked potentials (SSEP's) was investigated in a feline model of intracranial hypertension. Threshold values of cerebral perfusion pressure (CPP) and cerebral blood flow (CBF) required for maintenance of SSEP's are defined using a mathematical model. The model describes loss of amplitude of SSEP's using the form of a dose-response curve. Amplitude of the SSEP's declined to 50% of control values at a CBF of 15 ml/100 gm/min and a CPP of 20 mm Hg in the normoxic animal; in the presence of mild hypoxia (8 to 9 kPa), a significant increase in these values to 18 ml/100 gm/min and 32 mm Hg, respectively, occurred. No reliable changes in latency or central conduction time were demonstrated. It is concluded that given adequate oxygenation, evoked electrical activity is lost at too low a level of CPP for this parameter to be useful in clinical monitoring. However, even mild hypoxia, when combined with intracranial hypertension, produces a major risk to neuronal integrity.

Demonstration of neurovascular compression in trigeminal neuralgia with magnetic resonance imaging. Comparison with surgical findings in 52 consecutive operative cases.

Until recently, the inability to demonstrate neurovascular compression of the trigeminal nerve preoperatively resulted in surgery being offered only in cases of severe trigeminal neuralgia (TGN), frequently after a prolonged trial of medical treatment and following less invasive procedures, despite the fact that posterior fossa microvascular decompression gives long-term pain relief in 80% to 90% of cases. To assess whether vascular compression of the nerve could be demonstrated preoperatively, high definition magnetic resonance tomographic angiography (MRTA) was performed in 50 consecutive patients, five of whom had bilateral TGN, prior to posterior fossa surgery. The imaging results were compared with the operative findings in all patients, including two patients who underwent bilateral exploration. Vascular compression of the trigeminal nerve was identified in 42 of 45 patients with unilateral symptoms and on both sides in four patients with bilateral TGN. In the last patient with bilateral TGN, neurovascular compression was identified on one side, and on the other side the compressing superior cerebellar artery was separated from the nerve by a sponge placed during previous surgery. There was full agreement regarding the presence or absence of neurovascular compression demonstrated by MRTA in 50 of 52 explorations, but MRTA misclassified four vessels compressing the trigeminal nerve as arteries rather than veins. In two cases, there was disagreement between the surgical and MRTA findings. In the first of these cases, surgery revealed distortion of the nerve at the pons by a vein that MRTA had predicted to lie 6 mm remote from this point. In the second patient, venous compression was missed; however, this patient was investigated early in the series and did not have gadolinium-enhanced imaging. In nine cases, MRTA correctly identified neurovascular compression of the trigeminal nerve by two arteries. Moreover, MRTA successfully guided surgical reexploration in one patient in whom a compressing vessel was missed during earlier surgery and also prompted exploration of the posterior fossa in two patients with multiple sclerosis and one patient with Charcot-Marie-Tooth syndrome, in whom neurovascular compression was identified preoperatively. It is concluded that MRTA is an extremely sensitive and specific method for demonstrating vascular compression in TGN. As a result, open surgical procedures can be recommended with confidence, and microvascular decompression is now the treatment of choice for TGN at the authors' unit. They propose MRTA as the definitive investigation in such patients in whom surgery is contemplated.

Quantitative magnetic resonance imaging in consecutive patients evaluated for surgical treatment of temporal lobe epilepsy.

We present the results of quantitative Magnetic Resonance Imaging (MRI) in 55 consecutively referred patients with clinical evidence of temporal lobe epilepsy (TLE). The Cavalieri method was used in combination with point counting to provide unbiased estimates of the volume of the left and right hippocampus, amygdala, temporal lobe, lateral ventricles and cerebral hemisphere, and pixel by pixel maps of the T2 relaxation time were computed for both central and anterior sections of the hippocampus. The 99th centiles of hippocampal volume, hippocampal volume asymmetry and T2 relaxation times in 20 control subjects provided limits which identified the presence of MTS. The results of the quantitative MRI were compared with the results of conventional diagnostic MRI, foramen ovale (FO) recording and the WADA test. Thirty-one patients were found to have unilateral MTS (17 left and 14 right) and 7 bilateral MTS. No evidence of MTS was detected in 16 patients. Of the 31 patients diagnosed with unilateral MTS on the basis of hippocampal volume and T2 measurement, 74% and 77% would respectively have received the same diagnosis on the basis of hippocampal volume and T2 measurements alone. In comparison to FO recording, quantitative MRI has a sensitivity of 55% and a specificity of 86%, while conventional diagnostic MRI has a sensitivity of 42% and a specificity of 80% for detection of MTS. Unilateral abnormalities were detected by FO recording in 30% cent of patients who appeared normal on quantitative MRI. WADA test results were available for 40 patients. The findings were consistent with quantitative MRI showing reduced memory function ipsilateral to unilateral MTS in 18 patients, but reduced memory function contralateral to unilateral MTS in two patients, and reduced memory function without MR abnormality in seven patients. WADA testing revealed unilateral memory impairments where MRI found bilateral pathology in 4 patients and in 4 patients in whom quantitative MRI detected unilateral MTS there was no evidence of reduced memory during WADA testing of the corresponding cerebral hemisphere. In the patients with unilateral right MTS a highly significant negative correlation (p = 0.0003) was observed between age of onset and the volume of the contralateral temporal lobe. Quantitative MR imaging of the hippocampus (i.e. volume and T2 measurement) is preferable to conventional radiological reporting for providing objective evidence of the presence of MTS on which to base the referral of patients for surgery, and since it has associated morbidity FO recording is now only being used in selected patients. Furthermore, stereology provides a convenient method for estimating the volume of other brain structures, which is relevant to obtaining a better understanding of the effects of laterality and age of onset of TLE.

Quantification of tumour response to radiotherapy.

In 1979, the World Health Organization (WHO) established criteria based on tumour volume change for classifying response to therapy as (i) progressive disease (PD), (ii) partial recovery (PR), and (iii) no change (NC). Typically, the tumour volume is reported from diameter measurements, using the calliper method. Alternatively, the Cavalieri method provides unbiased volume estimates of any structure without assumptions about its shape. In this study, we applied the Cavalieri method in combination with point counting to investigate the changes in tumour volume in four patients with high grade glioma, using 3D MRI. In particular, the volume of tumour within the enhancement boundary, the enhancing abnormality (EA), was estimated from T(1) weighted images, and the volume of the non-enhancing abnormality, (NEA) enhancing abnormality, was estimated from T(2) relaxation time and magnetic transfer ratio tissue characterization maps. We compared changes in tumour volume estimated by the Cavalieri method with those obtained using the calliper method. Absolute tumour volume differed significantly between the two methods. Analysis of relative change in tumour volume, based on the WHO criteria, provided a different classification using the calliper and Cavalieri methods. The benefit of the Cavalieri method over the calliper method in the estimation of tumour volume is justified by the following factors. First, Cavalieri volume estimates are mathematically unbiased. Second, the Cavalieri method is highly efficient under an appropriate sampling density (i.e. EA volume estimates can be obtained with a coefficient of error no higher than 5% in 2-3 min). Third, the source of variation of the volume estimates due to disagreements between observers, and within observer, is much greater in the positioning of the calliper diameters than in the identification of the tumour boundaries when applying the Cavalieri method. Additionally, the error prediction formula, available to estimate the coefficient of error of Cavalieri volume estimates from the data, allows us to establish more precise classification criteria against which to identify potentially clinical significant changes in tumour volume.

Headshaking in horses: possible aetiopathogenesis suggested by the results of diagnostic tests and several treatment regimes used in 20 cases.

Twenty mature horses with typical headshaking of 2 week-7 year duration were studied. Clinical examinations included radiography of the head and nasopharyngeal endoscopy. All were assessed at rest and at exercise, both before and after fitting an occlusive nasal mask, application of tinted contact lenses and the perineural anaesthesia of the infraorbital and posterior ethmoidal branches of the trigeminal nerve. Infraorbital anaesthesia had no effect in 6/7 cases but 11/17 (65%) cases showed a 90-100% improvement following posterior ethmoidal nerve anaesthesia. Tinted contact lenses had no apparent long-term benefit, although 2 cases showed a transient improvement. We found no other evidence to suggest a photic aetiology in the current series of cases. Treatment regimens based on the results of the diagnostic investigative methods included sclerosis of the posterior ethmoidal branch of the trigeminal nerve. This was effective in some cases but the benefits were temporary. Cyproheptadine alone was ineffective but the addition of carbamazepine resulted in 80-100% improvement in 80% of cases. Carbemazepine alone was effective in 88% of cases but results were unpredictable at predefined dose rates. The positive response to carbamazepine, combined with the clinical features is consistent with involvement of the trigeminal nerve, particularly the more proximal branches such as the posterior ethmoidal nerve. Headshaking has some clinical features in common with trigeminal neuralgia in humans. As a result of the findings detailed in this paper, we conclude that a trigeminal neuritis or neuralgia may be the basis of the underlying aetiopathology of equine headshaking. Initial observations of the positive response of headshakers to carbamazepine therapy is encouraging. However, future studies will include a more detailed investigation of dosages, duration of effectiveness (in some cases it appears short-lived) and other effects. In practice there is a realistic possibility of controlling but not curing headshaking with carbamazepine therapy at the present time. Other future investigations will include details of the functional anatomy of the trigeminal nerve and the role of the P2 myelin protein in headshaking and other neurological disease.

Neurosurgery and facial pain.

This article reviews the diagnosis, differential diagnosis and management of trigeminal neuralgia, the commonest facial pain condition treated by the neurosurgeon. The advantages offered by microvascular decompression as a treatment are reviewed and compared with medical treatment and percutaneous techniques.

Effect of limb tourniquet on cerebral perfusion pressure in a head-injured patient.

Thirty percent of patients with severe head injury also have significant extracranial injuries. Treatment for these injuries should not be allowed to jeopardise the brain which is more susceptible to damage in these circumstances. A case is presented in which significant decrease in cerebral perfusion pressure occurred consequent upon use of a lower limb tourniquet.

The genetics of the sixth and seventh components of complement in the dog: polymorphism, linkage, locus duplication, and silent alleles.

The complement components C6 and C7 exhibit genetic polymorphism in the domestic dog. In the case of C6, there is a single locus with a null allele and two structural alleles; in the case of C7, there are two linked loci, each with three structural alleles. There is a null allele or locus deletion at one of these loci. In all cases, inheritance is autosomal and codominant. The C7 loci are closely linked to each other and to C6. This complex is not close to the dog major histocompatibility complex (MHC) locus.