Epilepsia partialis continua: A review.

Epilepsia partialis continua (EPC) is a rare type of focal motor seizure characterized by continuous, involuntary muscle contractions in a specific part of the body. These contractions usually involve rhythmic, twitching movements and can last for several hours to days. The seizures are usually limited to one part of the body and can be clonic or dystonic. EPC can affect people of all ages but is more common in children and adolescents. The pathophysiology of EPC is complex and depends on the cause. There are several possible causes of EPC including structural brain abnormalities, infections, metabolic and genetic disorders, inflammatory conditions, traumatic brain injury, and vascular causes. The work-up of EPC includes electroencephalography (EEG), magnetic resonance imaging (MRI) of the brain, position emission tomography (PET) scan of the brain, autoimmune antibodies, infection work-up, and metabolic and genetic work-up. The management of EPC can be challenging. Antiseizure medications (ASDs) including benzodiazepines are an integral part of the management of EPC. Immunotherapy trials are recommended in resistant cases. Epilepsy surgery is one of the effective modalities in some surgically amenable cases. This article reviews the topic of EPC and summarizes diagnostic and .treatment recommendations.

Transcranial direct current stimulation for focal status epilepticus or lateralized periodic discharges in four patients in a critical care setting.

OBJECTIVE: Transcranial direct current stimulation (tDCS) has been advocated for various neurological conditions, including epilepsy. A 1-4-mA cathodal current applied to the scalp over a seizure focus can reduce spikes and seizures. This series of four patients with focal status epilepticus is among the first case series to demonstrate benefit of tDCS in the critical care setting. METHODS: Patients in the intensive care unit were referred for tDCS treatment when focal status epilepticus or clinically relevant lateralized periodic discharges did not resolve with conventional antiseizure medications and anesthetics. Battery-powered direct cathodal current at 2 mA was delivered by an ActivaDose (Caputron) tDCS device via a saline-soaked sponge on the scalp over the seizure focus. Anode was on the contralateral forehead or shoulder. Treatment was for 30 min, repeated twice in a day, then again 1-4 times more over the next few days. RESULTS: Three females and one male, aged 34-68 years, were treated. Etiologies of status epilepticus were posterior reversible encephalopathy syndrome in association with immunosuppressants for a liver transplant, perinatal hypoxic-ischemic injury, a prior cardioembolic parietal stroke, and central nervous system lupus. tDCS led to significant reduction of interictal spikes (.78 to .38/s, p < .0001) in three cases and electrographic seizures (3.83/h to 0/h, p < .001) in two cases. Medication reductions were enabled in all cases subsequent to tDCS. The only side effect of tDCS was transient erythema under the sponge in one case. Two patients died of causes unrelated to tDCS, one was discharged to a nursing home, and one became fully responsive as seizures were controlled with tDCS. SIGNIFICANCE: Spikes and electrographic seizure frequency significantly improved within 1 day of tDCS. Results are potentially confounded by multiple ongoing changes in medications and treatments. These results might encourage further investigation of tDCS in the critical care setting, but verification by controlled studies will be required.

Temporal subcortical T2 hypointensity on MRI in epilepsia partialis continua, a non ketotic hyperglycemia rather than herpes encephalitis.

PURPOSE: Hyperglycemia can present as many neurological problems, one of them is seizure. Different brain MRI features can be seen in focal seizures associated with nonketotic hyperglycemia that subcortical T2 hypointensity is the only characteristic one. Finding this MRI feature is highly valuable in early diagnosis and treatment. METHODS: Our patient was a 60-year-old female, a case of type 2 diabetes mellitus. She was brought to Emergency Room (ER) with focal colonic status epilepticus of right face and arm associated with confusion and drowsiness progressed over 2 weeks prior to admission. At first, acyclovir was started alongside anti-seizure medication with doubt of herpes encephalitis but antiviral was discontinued after normal LP result and characteristic MRI features. RESULTS: Subcortical T2 hypointensity in left temporal and insular lobe was seen on first MRI that was resolved on follow up MRI after she was treated. CONCLUSION: Epilepsia partialis continua in the setting of non ketotic hyperglycemia should be differentiated from that in herpes encephalitis in a diabetic patient presenting with subacute confusional state and focal status epilepticus considering characteristic MRI finding of subcortical T2 hypointensity.

Sporadic Creutzfeldt-Jakob disease presenting as epilepsia partialis continua and non-ictal nystagmus.

BACKGROUND AND PURPOSE: Creutzfeldt-Jakob disease (CJD) is a rare form of rapidly progressive neurodegenerative disorder. Seizures are uncommon in the early stage of CJD, increasing diagnostic difficulty. METHODS: An autopsy-proven case of CJD presenting initially as an epilepsia partialis continua is reported, in which the initial workup was unremarkable. Retrospectively, the presence of nystagmus, which proved to be non-epileptic, pointed to a cerebellar lesion before a diagnosis of clinically probable CJD was made. RESULTS: A 70-year-old man presented with a 3-week history of intermittent rhythmic jerking tremors in his left limbs, interfering with his gait. Examination showed left body clonic movements. Electroencephalography revealed an ictal right centroparietal pattern of focal status epilepticus. Video-oculography revealed right-beating nystagmus (mean slow phase velocity [SPV] 3.4º/s) in the dark and left-beating nystagmus (SPV 2.6º/s) in the light, left-beating nystagmus after head shaking (SPV 4º/s) and during mastoid vibration (SPV 11º/s) and mildly hypoactive horizontal head impulses. Search for occult malignancy, serologies, cerebrospinal fluid analyses, anti-onconeural antigen, auto-immune panel and brain magnetic resonance imaging were unrevealing. Rapid neurological decline was observed. Three weeks later, cerebrospinal fluid was positive for 14.3.3 protein, electroencephalography showed generalized periodic sharp wave complexes and brain magnetic resonance imaging revealed diffusion restriction and T2/fluid-attenuated inversion recovery hyperintensities in the cerebellum, basal ganglia, thalamus and cortex. He died 1 month later. Neuropathological study confirmed the diagnosis of CJD. CONCLUSION: This case highlights that CJD should be considered in the differential diagnosis of new onset epilepsia partialis continua and that neuro-ophthalmological examination can be helpful in pointing to early asymmetric cerebellar involvement.

'Hand mechanogram' in epilepsia partialis continua.

Epilepsia partialis continua manifests as low-frequency, rhythmic involuntary movements of a focal body part. We report a young man, HIV-positive and with syphilis, who developed right-hand epilepsia partialis continua associated with a small left-sided cortico-subcortical frontal lesion. A pen and paper test provided 'mechanographic' data on frequency, amplitude and rhythmicity of the hand movements, helping distinguish it from other causes of low-frequency repetitive hand movements.

Epilepsia partialis continua revealing idelalisib-associated PML-IRIS: clinical and pathological features.

Idelalisib, a selective phosphatidylinositol 3-kinase delta (PI3Kδ) inhibitor, is a newly approved second-line drug for patients with chronic lymphocytic leukemia. Recent clinical trials have suggested a possible association between idelalisib treatment and development of progressive multifocal leukoencephalopathy (PML) due to John Cunningham virus (JCV) reactivation. Nevertheless, clinical course and radiological and pathological features of idelalisib-induced PML still need to be clarified. We provide here the first clinicopathological description of idelalisib-associated PML in a patient who developed epilepsia partialis continua (EPC) as the first manifestation of the disease. Since EPC could present without electroencephalogram alterations, it is crucial to recognize the clinical features of this epileptic condition. EPC is characterized by the presence of repetitive, irregular, clonic jerking, often associated with hemiparesis and involvement of distal rather than proximal muscle groups. Moreover, we highlight the importance of brain biopsy in selected cases when there is a high clinical suspicion of PML, despite negative JCV testing in the cerebrospinal fluid. The pathological finding of prominent inflammatory infiltrate observed here was consistent with a diagnosis of immune reconstitution inflammatory syndrome (IRIS). IRIS is often associated with PML as a paradoxical worsening of clinical symptoms due to an overreacting immune response, in the context of previous immunosuppression. The unprecedented pathologic observation of IRIS in idelalisib-associated PML provides further insights into the pathogenesis of this rare neurological side effect.

Diagnostic algorithm for children presenting with epilepsia partialis continua.

OBJECTIVE: To characterize a cohort of children with epilepsia partialis continua (EPC) and develop a diagnostic algorithm incorporating key differential diagnoses. METHODS: Children presenting with EPC to a tertiary pediatric neurology center between 2002 and 2019 were characterized. RESULTS: Fifty-four children fulfilled EPC criteria. Median age at onset was 7 years (range 0.6-15), with median follow-up of 4.3 years (range 0.2-16). The diagnosis was Rasmussen encephalitis (RE) in 30 of 54 (56%), a mitochondrial disorder in 12 of 54 (22.2%), and magnetic resonance imaging (MRI) lesion-positive focal epilepsy in 6 of 54 (11.1%). No diagnosis was made in 5 of 54 (9%). Children with mitochondrial disorders developed EPC earlier; each additional year at presentation reduced the odds of a mitochondrial diagnosis by 26% (P = .02). Preceding developmental concerns (odds ratio [OR] 22, P < .001), no seizures prior to EPC (OR 22, P < .001), bilateral slowing on electroencephalogram (EEG) (OR 26, P < .001), and increased cerebrospinal fluid (CSF) protein level (OR 16) predicted a mitochondrial disorder. Asymmetry or hemiatrophy was evident on MRI at presentation with EPC in 18 of 30 (60%) children with RE, and in the remainder at a median of 6 months (range 3-15) after EPC onset. The first diagnostic test is brain MRI. Hemiatrophy may permit a diagnosis of RE with unilateral clinical and EEG findings. For children in whom a diagnosis of RE cannot be made on first scan but the clinical and radiological presentation resembles RE, repeat imaging every 6 months is recommended to detect progressive unicortical hemiatrophy, and brain biopsy should be considered. Evidence of intrathecal inflammation (oligoclonal bands and raised neopterin) can be supportive. In children with bihemispheric EPC, rapid polymerase gamma testing is recommended and if negative, sequencing mtDNA and whole-exome sequencing on blood-derived DNA should be performed. SIGNIFICANCE: Children presenting with EPC due to a mitochondrial disorder show clinical features distinguishing them from RE and structural epilepsies. A diagnostic algorithm for children with EPC will allow targeted investigation and timely diagnosis.

Epilepsia partialis continua following a Western variant tick-borne encephalitis.

Epilepsia partialis continua (EPC) is a rare entity, first described in 1894 by Kozevnikov, as a variant of simple focal motor status epilepticus. EPC is most frequently characterized by motor symptoms, but as recently described, non-motor manifestations may occur, such as somatosensory symptoms or aura continua. EPC in adults has been attributed to various etiologies: infectious, vascular, neoplastic, and metabolic. According to the recent definition, we reported a case of EPC with behavioral symptoms, following a tick-borne encephalitis (TBE) contracted in an endemic area (North Eastern Italy). Patient's symptom was a poorly localized "whole body sensation", which is reported as a condition occurring only in frontal lobe epilepsy. Patient's EEG showed a left frontal predominance of epileptiform discharges. Literature highlighted the importance of the Far-eastern TBE variant as a cause of EPC, since no Western variant TBE cases are reported. In contrast to what was claimed so far, our case demonstrates that not only the Far-eastern TBE variant, but also Western variant TBE is a cause of EPC. Prognosis of EPC depends largely on the underlying etiology, and it is frequently drug-resistant. Our patient was treated with intravenous levetiracetam, with a subsequent clinical recovery and a disappearance of epileptiform discharges. The rapid clinic and electroencephalographic response to levetiracetam confirm that it can be a promising therapeutic option for treatment of EPC.

People with epilepsy are diagnosed most often with unspecified epilepsy, followed by focal epilepsy, generalized convulsive epilepsy, and generalized nonconvulsive epilepsy-US MarketScan data, 2010-2015.

The distribution of epilepsy types varies by age, etiology, provider diagnostic capabilities, and assessment criteria. No recent US study has examined the distribution of epilepsy types in a large, population-based sample of people with epilepsy. We used MarketScan data from January 1, 2010 through September 30, 2015, to estimate the proportion of epilepsy types among all (N=370,570) individuals diagnosed with epilepsy. We identified cases of epilepsy as individuals with at least one International Classification of Disease, 9th version (ICD-9) diagnostic code of 345.X and the use of at least one antiseizure drug described in the 2015 MarketScan Redbook. Unspecified epilepsy was more common (36.8%) than focal-localized epilepsy (24.6%), generalized convulsive epilepsy (23.8%), generalized nonconvulsive epilepsy (8.9%), other forms of epilepsy (5.2%), infantile spasm (0.3%), and epilepsia partialis continua (0.3%). The high proportion of epilepsy classified as unspecified might be lowered by improved training in epilepsy diagnosis and coding.

Bottom-of-sulcus focal cortical dysplasia presenting as epilepsia partialis continua multimodality characterization including 7T MRI.

INTRODUCTION: Bottom-of-sulcus focal cortical dysplasias are an under recognized, surgically treatable cause of focal epilepsy. Resection can dramatically reduce the seizure burden for children with refractory epilepsy, or eliminate seizures altogether. MATERIAL AND METHODS: We report the case and present the results of multimodality evaluation of a 15-year-old young man who presented with long-standing partial epilepsy affecting his right leg, which over the years became refractory to therapy. RESULTS: High-resolution 3T MRI images acquired as a dedicated epilepsyprotocol were initially interpreted as unremarkable. On further review by an experienced specialist aware of clinical and electroencephalographic findings, a subtle focal cortical dysplasia was identified at the bottom of a sulcus near the medial aspect of the left precentral gyrus. After confirmation of the extent of the lesion with PET and ultra-high field 7T MRI, the patient underwent cortical mapping and focal resection and remains free of seizures. COCLUSIONS: This case emphasizes the need for a multidisciplinary approach to the evaluation of refractory focal epilepsy in children and highlights the potential role of ultra-high field 7T MRI in identifying the often subtle causative anatomic abnormalities.

[Rasmussen syndrome: a clinicopathologic study of four cases].

Objective: To investigate the clinicopathologic features of Rasmussen syndrome (RS) and to raise awareness of this rare disease. Methods: Clinicopathologic data of 4 cases of RS were retrospectively analyzed at Beijing Haidian Hospital from 2008 to 2016. Results: The clinical manifestations included epilepsia partialis continua and progressive neurologic deficits in all patients.MRI demonstrated unihemispheric focal cortical atrophy in all cases. The histopathologic changes included variable degrees of lymphocytic infiltrate within the cortex, subarachnoid space and perivascular cuffing.Microglial nodules and neuronophagia were seen. Mild to severe neuronal loss was noted with variable degrees of reactive gliosis. Spongy edema and cavitation were observed in focal cortex. Inflammation involving hippocampus was seen in one case. Three cases were accompanied by focal cortical dysplasia (FCD) Ⅲd. Immunohistochemical staining showed that the infiltrative lymphocytes were positive for CD3, CD8, granzyme B and TIA1 and the proliferating microglial cells were positive for CD68. NeuN positive neurons decreased significantly and reactive astrocytes were GFAP positive. Conclusions: Pathologic changes of RS are similar to viral encephalitis and the inflammation is progressive and multifocal involving the hemisphere. The diagnosis of RS relies on pathologic features combined with clinical findings and neuroradiological examinations.

[Etiology and clinical features of epilepsia partialis continua: an analysis of six cases].

OBJECTIVE: To investigate the etiology and clinical features of epilepsia partialis continua (EPC) in children. METHODS: A retrospective analysis was performed for the clinical features, diagnosis and treatment of six children with EPC, and the clinical and laboratory features and prognosis were compared between the children with different etiologies. RESULTS: There were five girls and one boy, with an onset age ranging from one year and seven months to nine years. Two were diagnosed with Rasmussen encephalitis, one was diagnosed with focal cortical dysplasia, one was diagnosed with Alpers syndrome caused by POLG gene mutation, one was diagnosed with Angelman syndrome, and one was diagnosed with tuberculous meningitis. The latter two children had the predisposing factors for acute encephalopathy induced by status epilepticus and craniocerebral operation during the onset of EPC, while the other four children had natural progression of EPC. All the children had focal seizures except EPC, and symptoms included automatism, bilateral asymmetric tonic seizure, deflection, complex motor, and autonomic symptoms, with disturbance of consciousness in some children. EPC often lasted for several days or even several months. All children had abnormalities on head MRI, including local abnormal signal, cortex swelling, diffusive brain atrophy or brain atrophy at one side, local cortex thickening, and cortical necrosis. Head PET/CT scan was performed for three children and found local hypermetabolism or co-existence of hypermetabolism and hypometabolism. All the children had abnormalities on electroencephalography (EEG), with cerebral, hemispheric, or diffusive distribution of abnormal electrical activities, and during the onset of EPC, some EEG changes were recognizable and some were difficult to identify. All the children with EPC were not sensitive to antiepileptic drugs. EPC was relatively self-limiting in the child with Angelman syndrome. The child with focal cortical dysplasia underwent resection of epileptic foci and had good postoperative control, without neurological dysfunction. The child with Rasmussen encephalitis underwent functional hemispherectomy and had no attack after surgery, with neurological dysfunction. The child with Alpers syndrome had the worst prognosis. CONCLUSIONS: EPC is a special type of epileptic seizures. Immune inflammation and metabolic etiologies are the main causes of EPC in children, and the selection of treatment regimens, treatment outcome, and prognosis depend on etiology.

Epilepsia partialis continua after an anterior circulation ischaemic stroke.

BACKGROUND AND PURPOSE: Although cerebrovascular disorders are the main cause of epilepsia partialis continua (EPC) in adulthood, the frequency of EPC after stroke is unknown. The aim was to prospectively ascertain its frequency 1 year after an ischaemic stroke. METHODS: This was a prospective study of consecutive acute anterior circulation ischaemic stroke patients, previously independent, with an admission National Institutes of Health Stroke Scale score ≥4, an acute ischaemic lesion on imaging and no previous epileptic seizures. During admission patients received standardized diagnostic and medical care and were submitted to a neurophysiological evaluation protocol. One year after stroke, patients were re-evaluated by an epilepsy expert neurologist and performed a video-electroencephalogram with electromyography co-registration whenever myoclonus was observed during neurological examination for jerk-locked back averaging analysis (JLBA). EPC was defined as continuously repeated fragments of epileptic seizures, with preserved consciousness, lasting at least 1 h, and representing locally restricted epileptic activity. RESULTS: In all, 151 acute anterior circulation stroke patients were consecutively included and prospectively evaluated, but 23 died in the first year. One year after stroke, from 127 patients alive, 117 (92.1%) underwent clinical and neurophysiological evaluation. In two (1.7%) patients, EPC diagnosis was made both by clinical and electroencephalographic criteria, namely JLBA. Both patients had a history of remote symptomatic seizures and one of them acute symptomatic seizures and non-convulsive status epilepticus criteria during the first 7 days after stroke. CONCLUSIONS: Despite its low frequency, the high stroke incidence makes post-stroke EPC relevant. This study draws attention to this recognizable condition with therapeutic and eventually prognostic implications.

Safety of repetitive transcranial magnetic stimulation in patients with epilepsy: A systematic review.

Approximately one-third of patients with epilepsy remain with pharmacologically intractable seizures. An emerging therapeutic modality for seizure suppression is repetitive transcranial magnetic stimulation (rTMS). Despite being considered a safe technique, rTMS carries the risk of inducing seizures, among other milder adverse events, and thus, its safety in the population with epilepsy should be continuously assessed. We performed an updated systematic review on the safety and tolerability of rTMS in patients with epilepsy, similar to a previous report published in 2007 (Bae EH, Schrader LM, Machii K, Alonso-Alonso M, Riviello JJ, Pascual-Leone A, Rotenberg A. Safety and tolerability of repetitive transcranial magnetic stimulation in patients with epilepsy: a review of the literature. Epilepsy Behav. 2007; 10 (4): 521-8), and estimated the risk of seizures and other adverse events during or shortly after rTMS application. We searched the literature for reports of rTMS being applied on patients with epilepsy, with no time or language restrictions, and obtained studies published from January 1990 to August 2015. A total of 46 publications were identified, of which 16 were new studies published after the previous safety review of 2007. We noted the total number of subjects with epilepsy undergoing rTMS, medication usage, incidence of adverse events, and rTMS protocol parameters: frequency, intensity, total number of stimuli, train duration, intertrain intervals, coil type, and stimulation site. Our main data analysis included separate calculations for crude per subject risk of seizure and other adverse events, as well as risk per 1000 stimuli. We also performed an exploratory, secondary analysis on the risk of seizure and other adverse events according to the type of coil used (figure-of-8 or circular), stimulation frequency (≤ 1 Hz or > 1 Hz), pulse intensity in terms of motor threshold (<100% or ≥ 100%), and number of stimuli per session (< 500 or ≥ 500). Presence or absence of adverse events was reported in 40 studies (n = 426 subjects). A total of 78 (18.3%) subjects reported adverse events, of which 85% were mild. Headache or dizziness was the most common one, occurring in 8.9%. We found a crude per subject seizure risk of 2.9% (95% CI: 1.3-4.5), given that 12 subjects reported seizures out of 410 subjects included in the analysis after data of patients with epilepsia partialis continua or status epilepticus were excluded from the estimate. Only one of the reported seizures was considered atypical in terms of the clinical characteristics of the patients' baseline seizures. The atypical seizure happened during high-frequency rTMS with maximum stimulator output for speech arrest, clinically arising from the region of stimulation. Although we estimated a larger crude per subject seizure risk compared with the previous safety review, the corresponding confidence intervals contained both risks. Furthermore, the exclusive case of atypical seizure was the same as reported in the previous report. We conclude that the risk of seizure induction in patients with epilepsy undergoing rTMS is small and that the risk of other adverse events is similar to that of rTMS applied to other conditions and to healthy subjects. Our results should be interpreted with caution, given the need for adjusted analysis controlling for potential confounders, such as baseline seizure frequency. The similarity between the safety profiles of rTMS applied to the population with epilepsy and to individuals without epilepsy supports further investigation of rTMS as a therapy for seizure suppression.

Epilepsia partialis continua responsive to neocortical electrical stimulation.

Epilepsia partialis continua (EPC), defined as a syndrome of continuous focal jerking, is a rare form of focal status epilepticus that usually affects a distal limb, and when prolonged, can produce long-lasting deficits in limb function. Substantial electrophysiologic evidence links the origin of EPC to the motor cortex; thus surgical resection carries the risk of significant handicap. We present two patients with focal, drug-resistant EPC, who were admitted for intracranial video-electroencephalography monitoring to elucidate the location of the epileptogenic focus and identification of eloquent motor cortex with functional mapping. In both cases, the focus resided at or near eloquent motor cortex and therefore precluded resective surgery. Chronic cortical stimulation delivered through subdural strips at the seizure focus (continuous stimulation at 60-130 Hz, 2-3 mA) resulted in >90% reduction in seizures and abolition of the EPC after a follow-up of 22 months in both patients. Following permanent implantation of cortical stimulators, no adverse effects were noted. EPC restarted when intensity was reduced or batteries depleted. Battery replacement restored previous improvement. This two-case report opens up avenues for the treatment of this debilitating condition.

Epilepsia partialis continua of the abdominal muscles due to cerebrovascular disease.

Two elderly men, with previous history of cerebrovascular disease, were admitted to the emergency department due to focal motor status epilepticus with persistent myoclonic jerks of one side of the body. In both cases, the clinical picture evolved into a unilateral and isolated arrhythmic myoclonus of the abdominal muscles with preserved consciousness. These involuntary movements resolved with antiepileptic drugs. Although cerebrovascular disease is one of the most common causes of epilepsia partialis continua, reported cases in the literature with predominant abdominal involvement have a different aetiology. The neuroimaging and electroencephalographic findings showed a wide spectrum of different localizations and aetiologies associated with this particular type of epileptic seizure. Indeed, the pathophysiology of focal motor seizures involving the abdominal muscles is still a matter of discussion. In our second case, we present a patient with epilepsia partialis continua of the abdominal wall with an occipital focus, which, to the best of our knowledge, has not been previously reported. [Published with video sequences].

Comparative analysis of explanted DBS electrodes.

BACKGROUND: Hardware-related complications frequently occur in deep brain stimulation. Microscopy and spectroscopy techniques are effective methods for characterizing the morphological and chemical basis of malfunctioning DBS electrodes. A previous report by our team revealed the morphological and chemical alterations on a malfunctioning explanted electrode when it was compared to a new device. The aim of this preliminary study was to verify whether these morphological and chemical alterations in the materials were a direct result of the hardware malfunctioning or if the failure was correlated to a degradation process over time. METHODS: Two DBS electrodes were removed from two patients for reasons other than DBS system impairment and were analyzed by a scanning electron microscope and by an energy-dispersive X-ray spectroscopy. The results were compared to a malfunctioning device and to a new device, previously analyzed by our group. RESULTS: The analysis revealed that the wear of the polyurethane external part of all the electrodes was directly correlated with the duration of implantation period. Moreover, these alterations were independent from the electrodes functioning and from parameters used during therapy. CONCLUSIONS: This is the first study done that demonstrates a time-related degradation in the external layer of DBS electrodes. The analyses of morphological and chemical properties of the implanted devices are relevant for predicting the possibility of hardware's impairment as well as to improve the bio-stability of DBS systems.