Multipoint fixation with vascularised fibular bone graft and myotomy for atlanto-axial instability in cervical dystonia: a case report.

Spinal instability is a challenging condition to manage in patients with cervical dystonia. Standard surgical stabilisation approaches may fail to cope with additional stress forces created by spasmodic muscles leading to construct failure either in the immediate or late post-operative period. Long-term stabilisation relies on the management of dystonic symptoms and adjunctive strategies to increase fusion success rate. We discuss the management of a challenging patient with translational C1/2 instability who had three metalwork failures with standard occipito-cervical fixation techniques within a 12 month period. A combined surgical approach using multipoint fixation, sternocleidomastoid myotomy and a vascularised fibular occiput-C2 bone graft successfully prevented further metalwork failure at over 2 years follow up.

Endoscopic Endonasal Surgery for Resection of a Pterygopalatine Fossa Malignant Peripheral Nerve Sheath Tumor: 2-Dimensional Operative Video.

The pterygopalatine fossa (PPF) is an inverted, pyramid-shaped space immediately behind the posterior wall of the maxillary sinus, and lesions arising here include juvenile angiofibromas, schwannomas, and, in exceptionally rare cases, malignant peripheral nerve sheath tumors.1,2 Surgical access to the PPF is challenging and has been historically achieved via an open transmaxillary approach associated with facial scaring/deformity as well as potential injury to facial and infraorbital nerve branches.3 We present the case of a 67-year-old woman with facial numbness secondary to a presumed trigeminal schwannoma in the right PPF on magnetic resonance imaging. This surgical video highlights the key stages in performing an endoscopic endonasal excision of a PPF tumor. We start with a wide medial maxillary antrostomy, mobilization of the inferior turbinate, ethmoidectomy, and sphenoidotomy. The posterior wall of the maxillary sinus is then lifted off the anterior aspect of the tumor. The soft tissue attachment medial to the tumor containing the sphenopalatine artery is then cauterized and divided. This is followed by circumferential blunt dissection of the tumor until it is sufficiently mobile to remove in a piecemeal fashion. The PPF is then examined for any residual tumor and any bleeding from the maxillary artery within the fat pad. Hemostasis and reattachment of the inferior turbinate into the lateral nasal wall is demonstrated. The patient did not have any new deficits postoperatively, but histology indicated a malignant peripheral nerve sheath tumor and she underwent postoperative proton beam therapy. Postoperative surveillance magnetic resonance imaging at 14 months showed no tumor recurrence. The patient consented to the procedure in a standard fashion (Video 1).

Structural and molecular heterogeneity of calretinin-expressing interneurons in the rodent and primate striatum.

Calretinin-expressing (CR+) interneurons are the most common type of striatal interneuron in primates. However, because CR+ interneurons are relatively scarce in rodent striatum, little is known about their molecular and other properties, and they are typically excluded from models of striatal circuitry. Moreover, CR+ interneurons are often treated in models as a single homogenous population, despite previous descriptions of their heterogeneous structures and spatial distributions in rodents and primates. Here, we demonstrate that, in rodents, the combinatorial expression of secretagogin (Scgn), specificity protein 8 (SP8) and/or LIM homeobox protein 7 (Lhx7) separates striatal CR+ interneurons into three structurally and topographically distinct cell populations. The CR+/Scgn+/SP8+/Lhx7- interneurons are small-sized (typically 7-11 µm in somatic diameter), possess tortuous, partially spiny dendrites, and are rostrally biased in their positioning within striatum. The CR+/Scgn-/SP8-/Lhx7- interneurons are medium-sized (typically 12-15 µm), have bipolar dendrites, and are homogenously distributed throughout striatum. The CR+/Scgn-/SP8-/Lhx7+ interneurons are relatively large-sized (typically 12-20 µm), and have thick, infrequently branching dendrites. Furthermore, we provide the first in vivo electrophysiological recordings of identified CR+ interneurons, all of which were the CR+/Scgn-/SP8-/Lhx7- cell type. In the primate striatum, Scgn co-expression also identified a topographically distinct CR+ interneuron population with a rostral bias similar to that seen in both rats and mice. Taken together, these results suggest that striatal CR+ interneurons comprise at least three molecularly, structurally, and topographically distinct cell populations in rodents. These properties are partially conserved in primates, in which the relative abundance of CR+ interneurons suggests that they play a critical role in striatal microcircuits.

Secretagogin expression delineates functionally-specialized populations of striatal parvalbumin-containing interneurons.

Corticostriatal afferents can engage parvalbumin-expressing (PV+) interneurons to rapidly curtail the activity of striatal projection neurons (SPNs), thus shaping striatal output. Schemes of basal ganglia circuit dynamics generally consider striatal PV+ interneurons to be homogenous, despite considerable heterogeneity in both form and function. We demonstrate that the selective co-expression of another calcium-binding protein, secretagogin (Scgn), separates PV+ interneurons in rat and primate striatum into two topographically-, physiologically- and structurally-distinct cell populations. In rats, these two interneuron populations differed in their firing rates, patterns and relationships with cortical oscillations in vivo. Moreover, the axons of identified PV+/Scgn+ interneurons preferentially targeted the somata of SPNs of the so-called 'direct pathway', whereas PV+/Scgn- interneurons preferentially targeted 'indirect pathway' SPNs. These two populations of interneurons could therefore provide a substrate through which either of the striatal output pathways can be rapidly and selectively inhibited to subsequently mediate the expression of behavioral routines.

Biographical sketch: Jason Brice.

This article is a biographical sketch of retired British neurosurgeon Jason Brice, who is a pioneer of deep brain stimulation and helped establish the Wessex Neurological Centre.

Stress-induced lipocalin-2 controls dendritic spine formation and neuronal activity in the amygdala.

Behavioural adaptation to psychological stress is dependent on neuronal plasticity and dysfunction at this cellular level may underlie the pathogenesis of affective disorders such as depression and post-traumatic stress disorder. Taking advantage of genome-wide microarray assay, we performed detailed studies of stress-affected transcripts in the amygdala - an area which forms part of the innate fear circuit in mammals. Having previously demonstrated the role of lipocalin-2 (Lcn-2) in promoting stress-induced changes in dendritic spine morphology/function and neuronal excitability in the mouse hippocampus, we show here that the Lcn-2 gene is one of the most highly upregulated transcripts detected by microarray analysis in the amygdala after acute restraint-induced psychological stress. This is associated with increased Lcn-2 protein synthesis, which is found on immunohistochemistry to be predominantly localised to neurons. Stress-naïve Lcn-2(-/-) mice show a higher spine density in the basolateral amygdala and a 2-fold higher rate of neuronal firing rate compared to wild-type mice. Unlike their wild-type counterparts, Lcn-2(-/-) mice did not show an increase in dendritic spine density in response to stress but did show a distinct pattern of spine morphology. Thus, amygdala-specific neuronal responses to Lcn-2 may represent a mechanism for behavioural adaptation to psychological stress.

Dyslipidaemia in chronic acquired distal axonal polyneuropathy.

The link between hypertriglyceridaemia (HTG) and/or hypercholesterolaemia (HCL) and neuropathy is uncertain. We retrospectively reviewed records of 100 consecutive patients investigated for acquired chronic axonal distal polyneuropathy of unknown cause. Findings were compared with those of 102 consecutive controls. Patients with idiopathic neuropathy were subsequently compared with age- and gender-matched controls. There were more neuropathy patients than controls with HCL, defined as cholesterol levels >5 mmol/L (63 vs. 45.1%; p = 0.011). Neuropathy patients also had higher cholesterol levels than controls (p = 0.04). Cholesterol-lowering drug usage was similar in both groups. HTG (defined as >2 mmol/L) and triglyceride levels were comparable in both groups. HTG ranged from 2.1-4.2 mmol/L in neuropathy patients. A cause for neuropathy was identified in 59 patients. Thirty-one had impaired glucose metabolism. Forty-one had idiopathic neuropathy. No link was demonstrated between idiopathic neuropathy or painful idiopathic neuropathy, and HTG/HCL. Mean triglyceride and cholesterol levels in patients with idiopathic neuropathy were comparable to those of controls. HTG was significantly more common (p = 0.027), and triglyceride levels significantly higher (p = 0.005) in patients with neuropathy due to diabetes/impaired glucose tolerance (IGT)/alcoholism, than in patients with neuropathy of any other cause. These results suggest HCL >5 mmol/L may represent a cofactor contributing to presence of neuropathy irrespective of the underlying cause. They on the other hand do not support mild/moderate HTG as an independent cause of neuropathy. HTG is common in patients with neuropathy associated with diabetes/IGT/chronic alcoholism, where it may play a role in peripheral nerve damage. As previously reported, IGT was in our cohort frequent, present in one case in three, in the absence of another identifiable aetiology.

Restless legs syndrome in chronic inflammatory demyelinating polyneuropathy.

The prevalence of restless legs syndrome (RLS) is unknown in chronic inflammatory demyelinating polyneuropathy (CIDP). We prospectively studied 28 patients with CIDP. Prevalence of RLS in CIDP was ascertained by face-to-face interview using validated criteria and compared with that in 28 age- and gender-matched controls. Eleven (39.3%) CIDP patients were diagnosed with RLS, compared with 2 (7.1%) controls (P < 0.01). A significant correlation was ascertained between presence of RLS and lower limb weakness, functional disability, and summated compound muscle action potential (CMAP). The prevalence of RLS in CIDP was significantly higher than in controls in our study population, approaching 40%. Screening for RLS in CIDP patients may be appropriate, particularly in those with weakness, disability, and motor axonal loss in the lower limbs. Our findings may otherwise suggest the existence of peripheral components to the pathophysiology of RLS in patients with CIDP.

Deep brain stimulation: technology at the cutting edge.

Deep brain stimulation (DBS) surgery has been performed in over 75,000 people worldwide, and has been shown to be an effective treatment for Parkinson's disease, tremor, dystonia, epilepsy, depression, Tourette's syndrome, and obsessive compulsive disorder. We review current and emerging evidence for the role of DBS in the management of a range of neurological and psychiatric conditions, and discuss the technical and practical aspects of performing DBS surgery. In the future, evolution of DBS technology may depend on several key areas, including better scientific understanding of its underlying mechanism of action, advances in high-spatial resolution imaging and development of novel electrophysiological and neurotransmitter microsensor systems. Such developments could form the basis of an intelligent closed-loop DBS system with feedback-guided neuromodulation to optimize both electrode placement and therapeutic efficacy.