Epilepsy Surgery in Young Children With Tuberous Sclerosis Complex: A Novel Hybrid Multimodal Surgical Approach

BACKGROUND

Surgery has become integral in treating children with tuberous sclerosis complex (TSC)-related drug-resistant epilepsy (DRE).

OBJECTIVE

To describe outcomes of a multimodal diagnostic and therapeutic approach comprising invasive intracranial monitoring and surgical treatment and compare the complementary techniques of open resection and magnetic resonance-guided laser interstitial thermal therapy.

METHODS

Clinical and radiographic data were prospectively collected for pediatric patients undergoing surgical evaluation for TSC-related DRE at our tertiary academic hospital. Seizure freedom, developmental improvement, and Engel class were compared.

RESULTS

Thirty-eight patients (20 females) underwent treatment in January 2016 to April 2019. Thirty-five underwent phase II invasive monitoring with intracranial electrodes: 24 stereoencephalography, 9 craniotomy for grid/electrode placement, and 2 grids + stereoencephalography. With the multimodal approach, 33/38 patients (87%) achieved >50% seizure freedom of the targeted seizure type after initial treatment; 6/9 requiring secondary treatment and 2/2 requiring a third treatment achieved >50% freedom. The median Engel class was II at last follow-up (1.65 years), and 55% of patients were Engel class I/II. The mean age was lower for children undergoing open resection (2.4 vs 4.9 years, P = .04). Rates of >50% reduction in seizures (86% open resection vs 88% laser interstitial thermal therapy) and developmental improvement (86% open resection vs 83% magnetic resonance-guided laser interstitial thermal therapy) were similar.

CONCLUSION

This hybrid approach of using both open surgical and minimally invasive techniques is safe and effective in treating DRE secondary to TSC. Clinical trials focused on treatment method with longer follow-up are needed to determine the optimal candidates for each approach and compare the treatment modalities more effectively.

Evaluation of cervical spine pathology in children with Loeys-Dietz syndrome

Background:

Loeys-Dietz syndrome (LDS) is a genetic connective tissue disorder associated with multiple musculoskeletal anomalies, including cervical spine instability. We sought to examine the nature of imaging for cervical spine instability in children with LDS due to likely pathogenic or pathogenic variants in TGFBR1, TGFBR2, TGFB2, SMAD3, or TGFB3.

Methods:

A retrospective chart review was conducted, examining relevant data for all children with LDS screened at our institution from 2004 through 2021. Cervical spine X-rays were used to assess cervical instability, cervical lordosis, and basilar impression.

Results:

A total of 39 patients were identified; 16 underwent cervical spine screening (56.25% male). Median age at initial screening was 7 years (Q1-Q3: 3.75–14, range: 0.1–19). Six of 16 patients evaluated (37.5%) had radiographical evidence of cervical instability. Mean angles of cervical lordosis were 20° (SD = 14.1°, range = 4°–33°) and 17.3° (SD = 16.4°, range = 2°–41°), respectively. Three patients demonstrated radiographical basilar impression. Radiographic progression of cervical instability was seen in one case. All but two were managed conservatively with observation, one patient underwent surgical fixation and fusion of C1-2, the other underwent complex cervical reconstruction anterior and posterior instrumentation.

Conclusion:

Cervical spine evaluation is important in this cohort; we identified 37.5% had evidence of cervical spine instability, and many had concurrent spinal pathology. From our experience, we agree with the recent advisement for screening at diagnosis and for those previously diagnosed that have not undergone screening. Future study may outline more specific screening practices.

The role of blood product removal in intraventricular hemorrhage of prematurity: a meta-analysis of the clinical evidence

INTRODUCTION

Premature neonates have a high risk of intraventricular hemorrhage (IVH) at birth, the blood products of which activate inflammatory cascades that can cause hydrocephalus and long-term neurological morbidities and sequelae. However, there is no consensus for one treatment strategy. While the mainstay of treatment involves CSF diversion to reduce intracranial pressure, a number of interventions focus on blood product removal at various stages including extraventricular drains (EVD), intra-ventricular thrombolytics, drainage-irrigation-fibrinolytic therapy (DRIFT), and neuroendoscopic lavage (NEL).

METHODS

We performed a systematic review and meta-analysis to compare the risks and benefits commonly associated with active blood product removal treatment strategies. We searched MEDLINE, Embase, Scopus, Cochrane Library, and CINAHL databases through Dec 2020 for articles reporting on outcomes of EVDs, thrombolytics, DRIFT, and NEL. Outcomes of interest were rate of conversion to ventriculoperitoneal shunt (VPS), infection, mortality, secondary hemorrhage, and cognitive disability.

RESULTS

Of the 10,398 articles identified in the search, 23 full-text articles representing 22 cohorts and 530 patients were included for meta-analysis. These articles included retrospective, prospective, and randomized controlled studies on the use of EVDs (n = 7), thrombolytics (n = 8), DRIFT therapy (n = 3), and NEL (n = 5). Pooled rates of reported outcomes for EVD, thrombolytics, DRIFT, and NEL for ventriculoperitoneal shunt (VPS) placement were 51.1%, 43.3%, 34.3%, and 54.8%; for infection, 15.4%, 12.5%, 4.7%, and 11.0%; for mortality, 20.0%, 11.6%, 6.0%, and 4.9%; for secondary hemorrhage, 5.8%, 7.8%, 20.0%, and 6.9%; for cognitive impairment, 52.6%, 50.0%, 53.7%, and 50.9%. Meta-regression using type of treatment as a categorical covariate showed no effect of treatment modality on rate of VPS conversion or cognitive disability.

CONCLUSION

There was a significant effect of treatment modality on secondary hemorrhage and mortality; however, mortality was no longer significant after adjusting for year of publication. Re-hemorrhage rate was significantly higher for DRIFT (p < 0.001) but did not differ among the other modalities. NEL also had lower mortality relative to EVD (p < 0.001) and thrombolytics (p = 0.013), which was no longer significant after adjusting for year of publication. Thus, NEL appears to be safer than DRIFT in terms of risk of hemorrhage, and not different than other blood-product removal strategies in terms of mortality. Outcomes-in terms of shunting and cognitive impairment-did not differ. Later year of publication was predictive of lower rates of mortality, but not the other outcome variables. Further prospective and randomized studies will be necessary to directly compare NEL with other temporizing procedures.

Cerebellitis as a neurosurgical disease in pediatrics

The diagnostic evaluation and role of neurosurgery in the treatment of cerebellitis is unclear. We explore the diagnostic evaluation and subsequent role of neurosurgical intervention in pediatric cerebellitis in a case series, highlighting the diagnostic work up and treatments applied. A retrospective review was conducted of all pediatricpatients diagnosed with cerebellitis for whom neurosurgery was consulted at a single center from June 2008 to February 2019. Nine patients, four males (44.4%) and five females (55.6%) were identified. Common presenting symptoms were headache (n = 6, 66.7%), emesis (n = 5, 55.6%), and altered mental status (n = 4, 44.4%). Six (66.7%) had associated infections. Imaging abnormalities included tonsillar ectopia (n = 8, 88.9%), bilateral cerebellar T2 hyperintensity (n = 6, 66.7%), and obstructive hydrocephalus (n = 6, 66.7%). Management included antibiotics, antivirals, corticosteroids, mannitol, and hypertonic saline. Four (44.4%) required external ventricular drain (EVD) placement for a mean 11 days (SD 6.8, range 4-20) for hydrocephalus; none required additional neurosurgical interventions. Seven patients (77.8%) required ICU care for a mean 11.7 days (SD 14.0 range 1-42). At follow-up (mean 20.8 months, SD 28.7, range 0.6-64.9), two patients (n = 2, 22.2%) recovered completely, and six (66.7%) were functionally dependent (mRS > 2); the most common residual deficit was cognitive impairment (n = 5, 55.6%). Neurosurgical consultation should be considered in pediatric patients with cerebellitis. In our experience, temporary CSF diversion via an EVD is employed nearly half of the time. The presence of hydrocephalus requiring neurosurgical intervention may be a predictor of severe disease and poor outcome.

Staged Magnetic Resonance-Guided Laser Interstitial Thermal Therapy for Hypothalamic Hamartoma: Analysis of Ablation Volumes and Morphological Considerations

BACKGROUND

Hypothalamic hamartomas (HH) are a challenging pathology that cause gelastic seizures. Magnetic Resonance Imaging-guided Laser Interstitial Thermal Therapy (MRgLITT) offers a safe and effective treatment for HHs via a minimally invasive technique.

OBJECTIVE

To determine how clinical outcome correlates to residual tumor volume and surgical strategy by analyzing radiographic data and reconstructing volumetric imaging.

METHODS

Clinical and radiographic information of 58 pediatric patients who underwent MRgLITT for HH with at least 6 mo of follow-up were retrospectively reviewed. MR imaging was volumetrically reconstructed to analyze the impact of hamartoma and ablation volumes on outcome. Primary outcome measure was freedom from gelastic seizures.

RESULTS

Eighty-one percent of patients were completely free of gelastic seizures at last follow-up; of 22 patients with secondary nongelastic epilepsy, 15 were free of additional seizures. Postoperative complication rate was low. There was no significant difference in gelastic seizure outcome related to pre- or postoperative hamartoma size. Residual hamartoma percentage in those free of gelastic seizures was 43% compared to 71% in those with continued seizures (P = .021). Larger hamartomas required multiple ablations to achieve seizure freedom.

CONCLUSION

This large series of patients confirms the safety and efficacy of MRgLITT for pediatric HH and describes morphological considerations that predict success. Our data suggest that complete ablation of the lesion is not necessary, and that the focus should be on appropriate disconnection of the epileptogenic network. We have found that a staged approach to hamartoma ablation allows adequate disconnection of the hamartoma while mitigating risk to surrounding structures.

Predicting dysphagia in children undergoing surgery for posterior fossa tumors

PURPOSE

Posterior fossa tumors (PFTs) are the most common type of brain tumor in children. Dysphagia is a known complication of PFT resection in children, but data regarding risk factors and clinical course are sparse.

METHODS

The records of all children who underwent resection of posterior fossa tumor between April 2007 and May 2017 at our institution were analyzed. Clinical, radiographic, histologic data were gathered. Swallowing function was assessed immediately postoperatively and at 1-year follow-up.

RESULTS

A total of 197 patients were included. Forty-three (21.8%) patients developed dysphagia after surgery. Patients who developed dysphagia were younger (4.5 vs. 7.2 years, p < 0.01), were more likely to have brainstem compression (74.4% vs. 57.8%, p < 0.03) or invasion (14.0 vs. 9.7%, p < 0.03), and were more likely to have ependymoma (27.9% vs. 13.6%, p < 0.01) or ATRT (atypical teratoid/rhabdoid tumor) (9.3% vs. 3.9%, p < 0.01). Patients with postoperative dysphagia also had a longer length of stay (33.7 vs. 12.7 days, p < 0.01) and were more likely to be discharged to inpatient rehabilitation (25.6% vs. 9.1%, p < 0.01). Ten patients (5.1%) were PEG-dependent by 1-year follow-up. These patients were younger (2.7 vs. 5.6 years, p < 0.01), had a longer length of stay (55.5 vs. 27.4 days, p < 0.01), and were more likely to have ATRT (30.0% vs. 0.0%, p < 0.01). Recovery was not associated with tumor grade or extent of resection.

CONCLUSIONS

Dysphagia after PFT resection is associated with younger age, aggressive tumor histology, and increased healthcare utilization. While most patients recover, a small percentage are still dependent on enteral feeding at 1-year follow-up. Further research is needed to identify factors associated with persistent deficits.

Feasibility and safety of transradial access for pediatric neurointerventions

Background

Diagnostic cerebral angiograms are increasingly being performed by transradial access (TRA) in adults, following data from the coronary literature supporting fewer access-site complications. Despite this ongoing trend in neuroangiography, there has been no discussion of its use in the pediatric population. Pediatric TRA has scarcely been described even for coronary or other applications. This is the first dedicated large study of transradial access for neuroangiography in pediatric patients.

Methods

A multi-institutional series of consecutively performed pediatric transradial angiograms and interventions was collected. This included demographic, procedural, outcomes, and safety data. Data was prospectively recorded and retrospectively analyzed.

Results

Thirty-seven diagnostic angiograms and 24 interventions were performed in 47 pediatric patients. Mean age, height, and weight was 14.1 years, 158.6 cm, and 57.1 kg, respectively. The radial artery measured 2.09+/-0.54 mm distally, and 2.09+/-0.44 mm proximally. Proximal and distal angiography were performed for both diagnostic and interventional application (17 distal angiograms, two distal interventions). Clinically significant vasospasm occurred in eight patients (13.1%). Re-access was successfully performed 11 times in seven patients. Conversion to femoral access occurred in five cases (8.2%). The only access-related complication was a small asymptomatic wrist hematoma after TR band removal.

Conclusions

Transradial access in pediatric patients is safe and feasible. It can be performed successfully in many cases but carries some unique challenges compared with the adult population. Despite the challenge of higher rates of vasospasm and conversion to femoral access, it is worth exploring further, given the potential benefits.

Antiangiogenic agent as a novel treatment for pediatric intracranial arteriovenous malformations: case report

Intracerebral arteriovenous malformations (AVMs) are high-flow collections of abnormal vessels and a common cause of pediatric intracranial hemorrhage. There are few treatment options available for AVMs not amenable to surgical resection, endovascular embolization, radiosurgery, or multimodality treatment. The authors sought to review the molecular and genetic pathways that have been implicated in the formation of AVMs, focusing on the possibility of medically targeting these pathways in the treatment of AVMs. In the novel case presented here, a pediatric patient who was diagnosed with an intracranial AVM unamenable to conventional treatments underwent alternative treatment with molecular pathway inhibitors.

Advocacy in pediatric neurosurgery: results from a 2017 survey of the American Society of Pediatric Neurosurgeons

OBJECTIVE

Pediatric neurosurgeons are unswerving advocates for public health-related issues in children, with most providers participating in local, regional, national, or international efforts. Collective advocacy efforts by organized pediatric neurosurgeons have not been undertaken to date.

METHODS

A 10-item survey was administered to members of the American Society of Pediatric Neurosurgeons (ASPN) in order to evaluate attitudes and opinions regarding the development of a formal advocacy effort by the organization.

RESULTS

Seventy-nine of 178 registered members of the ASPN (44.38%) participated in the survey. Participants were 82.61% male, with age, stage of career, and practice type varied. Although there was unequivocal support for participation in organized advocacy, respondents were divided on methods and topics for advocacy. In this survey, the ASPN membership prioritized public health and clinical issues over economic issues that affected children.

CONCLUSIONS

Most respondents favored the drafting of position statements on key issues and partnerships with larger organizations to pursue an advocacy agenda. The survey provides data regarding pediatric neurosurgeons' attitudes that may assist with the design of a successful advocacy program.

Virtual surgical planning and 3D printing in repeat calvarial vault reconstruction for craniosynostosis: technical note

Repeat surgery for restenosis after initial nonsyndromic craniosynostosis intervention is sometimes needed. Calvarial vault reconstruction through a healed surgical bed adds a level of intraoperative complexity and may benefit from preoperative and intraoperative definitions of biometric and aesthetic norms. Computer-assisted design and manufacturing using 3D imaging allows the precise formulation of operative plans in anticipation of surgical intervention. 3D printing turns virtual plans into anatomical replicas, templates, or customized implants by using a variety of materials. The authors present a technical note illustrating the use of this technology: a repeat calvarial vault reconstruction that was planned and executed using computer-assisted design and 3D printed intraoperative guides.

Complete Resolution of Papilledema in Syndromic Craniosynostosis with Posterior Cranial Vault Distraction

We report a case of surgical management of Crouzon syndrome with multisuture craniosynostosis presenting with increased intracranial pressure (ICP) manifesting with chronic papilledema without ventriculomegaly. A 12-month-old boy had complete resolution of papilledema after posterior cranial vault distraction followed by staged fronto-orbital advancement. Expansion of the cranial vault with posterior distraction osteogenesis posed an elegant treatment, obviating ventriculoperitoneal shunt placement for cerebrospinal fluid (CSF) diversion. Strategies for the management of elevated ICP without ventriculomegaly in craniosynostosis include CSF shunting and cranial vault expansion. Posterior calvarial vault distraction associated with resolved papilledema has not been previously reported. Addressing the craniocephalic disproportion for this child with chronic papilledema, without ventriculomegaly, allowed the possibility of shunt freedom.

Stereotactic modulation of blood-brain barrier permeability to enhance drug delivery

Drug delivery in the CNS is limited by endothelial tight junctions forming the impermeable blood-brain barrier. The development of new treatment paradigms has previously been hampered by the restrictiveness of the blood-brain barrier to systemically administered therapeutics. With recent advances in stereotactic localization and noninvasive imaging, we have honed the ability to modulate, ablate, and rewire millimetric brain structures to precisely permeate the impregnable barrier. The wide range of focused radiations offers endless possibilities to disrupt endothelial permeability with different patterns and intensity following 3-dimensional coordinates offering a new world of possibilities to access the CNS, as well as to target therapies. We propose a review of the current state of knowledge in targeted drug delivery using noninvasive image-guided approaches. To this end, we focus on strategies currently used in clinics or in clinical trials such as targeted radiotherapy and magnetic resonance guided focused ultrasound, but also on more experimental approaches such as magnetically heated nanoparticles, electric fields, and lasers, techniques which demonstrated remarkable results both in vitro and in vivo. We envision that biodistribution and efficacy of systemically administered drugs will be enhanced with further developments of these promising strategies. Besides therapeutic applications, stereotactic platforms can be highly valuable in clinical applications for interventional strategies that can improve the targetability and efficacy of drugs and macromolecules. It is our hope that by showcasing and reviewing the current state of this field, we can lay the groundwork to guide future research in this realm.

Trends in epidemiology and hospitalization utilization for myelomeningocele repair from 2000 to 2009

PURPOSE

Although the incidence of myelomeningocele (MMC) has declined over the past decades with folic acid supplementation and prenatal screening, neural tube defects remain the most common birth defect in the USA. A majority of affected neonates require surgical repair. To characterize US trends in the epidemiology and hospital utilization of MMC repair over the past decade, we analyzed a nationally representative database.

METHODS

We queried the Healthcare Cost and Utilization Project (HCUP) Kid's Inpatient Database (KID) for all discharges with procedure code for MMC repair for the years 2000, 2003, 2006, and 2009. The cohorts from these time points were compared for their demographic and in-hospital variables. Results are reported as estimated frequencies and means with 95 % confidence intervals (CI).

RESULTS

Sex, race, insurance status, family income level, and mortality of affected infants have not changed significantly over the decade. A majority of neonatal MMC repairs occur in larger hospital bed size and more specialized children's hospital centers. Of patients, 52.3 to 60 % receive VPS placement during the same admission as the primary MMC repair. Total hospital costs for the MMC hospitalizations have remained relatively stable from 42,843 dollars in 2003 to 46,749 dollars in 2009 (adjusted to 2009 dollars).

CONCLUSION

Demographics of children having MMC repair have not changed significantly over the past decade, while these surgeries have become more concentrated in pediatric-specialized centers. There appears to be a plateau in public health and access advances with relatively stable cost of MMC hospital care.

Quality of the Patient Experience during Radiosurgery: Measurement toward Improvement

BACKGROUND

All physicians seek to improve the patient experience. In an awake surgical procedure, the patient has a unique opportunity to comment on all aspects of care. The provision of a positive experience is part of quality health care. Our purpose was to define this experience to determine areas for improvement.

METHODS

We evaluated 125 patients who underwent stereotactic radiosurgery using a frame-based, gamma knife technique. Patients were surveyed by a nurse practitioner across all elements of their procedural experience prior to same-day discharge.

RESULTS

The radiosurgery was completed in all patients with same-day discharge. In an initial 100-patient cohort, 89 patients said they had received adequate oral and/or intravenous sedation before the procedure. All 100 patients said that they felt comfortable before stereotactic frame application, and all patients later remembered frame application. These patients described frame application as very or adequately comfortable (n = 73), minimally uncomfortable (n = 18), or very uncomfortable (n = 9). Neuroimaging was described as very or adequately comfortable (n = 93), minimally uncomfortable (n = 3), or very uncomfortable (n = 4). Radiosurgery in the gamma knife unit was found to be very or adequately comfortable (n = 99) or very uncomfortable (n = 1). We evaluated how 8 separate factors may have contributed to survey responses related to procedural comfort. These factors included intravenous line placement, delivery of sedation medications, application of the head frame, having the MRI, having radiosurgery on the gamma knife bed, removal of the stereotactic frame, communication with caregivers, and knowing what to expect beforehand. We asked the patients to rate their nursing care during the radiosurgery experience, and 'excellent' was chosen by all initial 100 patients. Other elements of the procedure were also studied as well as suggestions for improvement. As a secondary objective, we then modified our protocol to include sodium bicarbonate added to the local anesthetic for frame application and evaluated an additional cohort of 25 patients.

CONCLUSIONS

Utilizing a system of physician and nursing education, together with pharmacological sedation and efficient procedural steps, patients said that intravenous line placement (91%), stereotactic frame application (74%), MRI (93%), receiving radiosurgery in the unit (99%), frame removal (84%), communication with caregivers (100%), and knowing what to expect beforehand (97%) were either very or adequately comfortable. Specific evaluations of care processes can lead to care improvement.

Aquaporin-4 gene variant independently associated with oedema after intracerebral haemorrhage

INTRODUCTION

Aquaporin-4 (AQP4) is the prominent water-channel protein in the brain playing a critical role in controlling cell water content. After intracerebral haemorrhage (ICH), perihematomal oedema (PHE) formation leads to a rapid increase in intracranial pressure (ICP) after the initial bleed. We sought to investigate the effect of a common genomic variant in the AQP4 gene on PHE formation after ICH.

METHODS

We reviewed the literature and identified a candidate polymorphism in AQP4 genes previously reported in Genome Wide Association Studies (GWAS). Between February 2009 and March 2011, 128 patients consented to genetic testing and were genotyped for single nucleotide polymorphism (SNP) on the AQP4 gene. Genomic DNA was extracted from buccal swabs using MasterAmp extraction kits (Epicentre, Madison, WI, USA). DNA extracted from buffy coats of whole blood samples was amplified via PCR. Linear regression with log-transformed ICH + PHE volume as the response variable was used to determine the association of SNP controlled for admission variables age, GCS, infratentorial location, hypertension, systolic blood pressure (SBP), blood urea nitrogen (BUN), glucose and alkaline phosphatase.

RESULTS

Nine of 128 patients had the minor allele for SNP rs1058427. Presence of the minor allele was significant in the model (P = 0.021), and associated with an increase of 88% in ICH + PHE volume (β = 0.632, exp(β) = 1.88) after controlling for admission variables. The only other significant variables included in the model was GCS (P < 0.001).

CONCLUSION

The establishment of an independent association between rs1054827 and ICH + PHE volume provides evidence implicating the AQP4 gene in haematoma and oedema formation after ICH. Further investigation is needed to characterise this link.

Underlying effect of age on outcome differences in arteriovenous malformation-associated intracerebral hemorrhage

Brain arteriovenous malformations (AVM) are the most common cause of intracerebral hemorrhage (ICH) in young adults. Although previous studies have found that the mortality and morbidity of ICH due to AVM (AVM-ICH) is lower than in spontaneous ICH, it is unclear whether the more favorable prognosis is directly related to the presence of the vascular malformation. We included 34 patients with AVM-ICH and 187 with spontaneous intracerebral hemorrhage (sICH) due to either hypertension or cerebral amyloid angiopathy. Patient data were obtained from the prospective Intracerebral Hemorrhage Outcomes Project, which enrolls ICH patients admitted to Columbia University Medical Center. Using ICH etiology (AVM-ICH or sICH) and previously verified predictors of ICH outcome, two multivariate analyses were performed with and without age to compare the odds of death at 3 months and the functional outcome. Although mortality in AVM-ICH group was lower than the sICH group (20.6% versus 43.3%, respectively), this value was only significant when age was excluded (p=0.017) and lost its significance when we controlled for age (p=0.157). There was an analogous loss of significance with functional outcome using the modified Rankin Scale. In conclusion, our data suggests that the previously observed lower case fatality rate and more favorable functional outcomes in the AVM-ICH group compared to the sICH group may largely be the result of age.

The quantified patient: a patient participatory culture

The Quantified Self Movement, which aims to improve various aspects of life and health through recording and reviewing daily activities and biometrics, is a new and upcoming practice of self monitoring that holds much promise. Now, the most underutilized resource in ambulatory health care, the patient, can participate like never before, and the patient's Quantified Self can be directly monitored and remotely accessed by health care professionals.

Use of liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) for routine identification of enzymatically digested proteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis

Automated liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) analysis of >100 tryptic digests carried out on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) separated, Coomassie Blue-stained proteins that were prepared by >50 different laboratories demonstrates that a commercial electrospray/quadrupole ion trap mass spectrometer and the tandem mass correlation algorithm developed by Eng et al. (Am. Soc. Mass Spectrom. 1994, 5, 976-989) provide an extremely robust and facile approach to routine protein identification. By requiring a minimum of two significant matches to peptides that would be predicted to be produced by the protease that was used, low pmol levels of proteins can be identified with high confidence while minimizing the probability of identifying the protease itself and/or the ubiquitous contaminant, keratin. Hence, in only 7% of the digests analyzed was keratin identified and in only 5% of the digests analyzed was the protease itself identified. In contrast, 58% of the analyzed samples were identified and, in many instances, multiple proteins were identified in the same sample. Although the median amount of digest analyzed was 6.1 pmol, the limit of sensitivity (as the instrument is configured with a flow rate of 4 microL/min) appears to be at the 500 fmol level. Since one of the primary reasons for not identifying a sample is that its sequence is not yet in the database searched, the utility of an LC MS/MS approach to protein identification will certainly increase in the future as the sequences of more genomes are completed.

Primary amino acid sequence of alpha-trichosanthin and molecular models for abrin A-chain and alpha-trichosanthin

Ricin A-chain, abrin A-chain, and alpha-trichosanthin are members of a larger group of proteins called ribosome-inactivating proteins. These proteins all function to catalytically inactivate eukaryotic 60 S ribosomal subunits leading to rapid shutdown of protein synthesis. They are homologous in sequence and are probably evolutionarily related. We have determined the complete primary amino acid sequence of alpha-trichosanthin and have found it to be homologous, as expected, to that of abrin A-chain and ricin A-chain. A crystal structure for ricin, which includes ricin A-chain and ricin B-chain, has been determined from x-ray diffraction data. Based on the sequence homologies of these proteins, we fit the primary sequences of abrin A-chain and alpha-trichosanthin to the backbone structure for ricin A-chain and have generated energy-minimized molecular models for them. These models should prove useful in studying the structural-functional relationships of these proteins in particular and of the class in general.