Aaron L. Cardon

An Update on Substance Use and Treatment following Traumatic Brain Injury

Traumatic brain injury (TBI) is a leading cause of mortality and morbidity among young adults. Substance abusers constitute a disproportionate percentage of these patients. A history of substance abuse predicts increased disability, poorer prognosis, and delayed recovery. While consensus in the literature indicates that substance‐abuse rates decline following injury, conflicting literature shows a significant history of brain injury in addicts. We reviewed the literature on substance abuse after TBI to explore the state of knowledge on TBI as a risk factor for substance abuse. While recent reviews regarding substance abuse in TBI patients concur that substance‐abuse rates decline even after mild TBI, an emerging literature suggests mild TBI may cause subtle impairments in cognitive, executive, and decision‐making functions that are often poorly recognized in early diagnosis and treatment. When combined with difficulties in psychosocial adjustment and coping skills, these impairments may increase the risk for chronic substance abuse in a subset of TBI patients. Preliminary results from veterans indicate these patterns hold in a combat‐related post‐traumatic stress disorder population with TBI. This increasingly prevalent combination presents a specific challenge in rehabilitation. While this comorbidity presents a challenge for the successful treatment and rehabilitation of both disorders, there is sparse evidence to recommend any specific treatment strategy for these individuals. Mild TBI and substance abuse are bidirectionally related both for risks and treatment. Further understanding the neuropsychiatric pathology and different effects of different types of injuries will likely improve the implementation of effective treatments for each of these two conditions.

TBC1D24 genotype–phenotype correlation: Epilepsies and other neurologic features

Objective: To evaluate the phenotypic spectrum associated with mutations in TBC1D24. Methods: We acquired new clinical, EEG, and neuroimaging data of 11 previously unreported and 37 published patients. TBC1D24 mutations, identified through various sequencing methods, can be found online (http://lovd.nl/TBC1D24). Results: Forty-eight patients were included (28 men, 20 women, average age 21 years) from 30 independent families. Eighteen patients (38%) had myoclonic epilepsies. The other patients carried diagnoses of focal (25%), multifocal (2%), generalized (4%), and unclassified epilepsy (6%), and early-onset epileptic encephalopathy (25%). Most patients had drug-resistant epilepsy. We detail EEG, neuroimaging, developmental, and cognitive features, treatment responsiveness, and physical examination. In silico evaluation revealed 7 different highly conserved motifs, with the most common pathogenic mutation located in the first. Neuronal outgrowth assays showed that some TBC1D24 mutations, associated with the most severe TBC1D24-associated disorders, are not necessarily the most disruptive to this gene function. Conclusions: TBC1D24-related epilepsy syndromes show marked phenotypic pleiotropy, with multisystem involvement and severity spectrum ranging from isolated deafness (not studied here), benign myoclonic epilepsy restricted to childhood with complete seizure control and normal intellect, to early-onset epileptic encephalopathy with severe developmental delay and early death. There is no distinct correlation with mutation type or location yet, but patterns are emerging. Given the phenotypic breadth observed, TBC1D24 mutation screening is indicated in a wide variety of epilepsies. A TBC1D24 consortium was formed to develop further research on this gene and its associated phenotypes.

Aromatic L-amino acid decarboxylase deficiency diagnosed by clinical metabolomic profiling of plasma

Aromatic L-amino acid decarboxylase (AADC) deficiency is an inborn error of metabolism affecting the biosynthesis of serotonin, dopamine, and catecholamines. We report a case of AADC deficiency that was detected using the Global MAPS platform. This is a novel platform that allows for parallel clinical testing of hundreds of metabolites in a single plasma specimen. It uses a state-of-the-art mass spectrometry platform, and the resulting spectra are compared against a library of ~2500 metabolites. Our patient is now a 4 year old boy initially seen at 11 months of age for developmental delay and hypotonia. Multiple tests had not yielded a diagnosis until exome sequencing revealed compound heterozygous variants of uncertain significance (VUS), c.286G>A (p.G96R) and c.260C>T (p.P87L) in the DDC gene, causal for AADC deficiency. CSF neurotransmitter analysis confirmed the diagnosis with elevated 3-methoxytyrosine (3-O-methyldopa). Metabolomic profiling was performed on plasma and revealed marked elevation in 3-methoxytyrosine (Z-score +6.1) consistent with the diagnosis of AADC deficiency. These results demonstrate that the Global MAPS platform is able to diagnose AADC deficiency from plasma. In summary, we report a novel and less invasive approach to diagnose AADC deficiency using plasma metabolomic profiling.

Diagnosis of adenylosuccinate lyase deficiency by metabolomic profiling in plasma reveals a phenotypic spectrum.

Adenylosuccinate lyase (ADSL) deficiency is a rare autosomal recessive neurometabolic disorder that presents with a broad-spectrum of neurological and physiological symptoms. The ADSL gene produces an enzyme with binary molecular roles in de novo purine synthesis and purine nucleotide recycling. The biochemical phenotype of ADSL deficiency, accumulation of SAICAr and succinyladenosine (S-Ado) in biofluids of affected individuals, serves as the traditional target for diagnosis with targeted quantitative urine purine analysis employed as the predominate method of detection. In this study, we report the diagnosis of ADSL deficiency using an alternative method, untargeted metabolomic profiling, an analytical scheme capable of generating semi-quantitative z-score values for over 1000 unique compounds in a single analysis of a specimen. Using this method to analyze plasma, we diagnosed ADSL deficiency in four patients and confirmed these findings with targeted quantitative biochemical analysis and molecular genetic testing. ADSL deficiency is part of a large a group of neurometabolic disorders, with a wide range of severity and sharing a broad differential diagnosis. This phenotypic similarity among these many inborn errors of metabolism (IEMs) has classically stood as a hurdle in their initial diagnosis and subsequent treatment. The findings presented here demonstrate the clinical utility of metabolomic profiling in the diagnosis of ADSL deficiency and highlights the potential of this technology in the diagnostic evaluation of individuals with neurologic phenotypes.

Should Repugnance Give Us Pause? On the Neuroscience of Daily Moral Reasoning

that, precisely for that reason, we should be allowed (and indeed encouraged) to use all available means to achieve the goal that is intrinsic to our existence (and particularly evident in sport). This normatively laden, and no doubt essentialist, understanding of the human is rather common among proponents of radical human enhancement. To give one last example, Nick Bostrom declares human nature to be “dynamic, partially human-made, and improvable” (2005b, 213), and infers from this that human dignity must consist in “what we are and what we have the potential to become.” The potential to become something other than we are is thus not only what makes us human, but also what gives us that special worth on which all our moral rights ultimately depend. Hence, to turn our backs on this potential would both violate our nature and compromise our dignity. Can an argument get any more essentialist than this?

Transverse Myelitis with Acute Inflammatory Polyradiculoneuropathy

A 15-year-old previously healthy female presented with lower extremity weakness and numbness, demonstrating imaging and laboratory characteristics diagnostic of both acute transverse myelitis (TM) and acute inflammatory demyelinating polyradiculopathy (AIDP). AIDP typically presents as a distinct clinical entity limited to the peripheral nervous system and nerve roots, but has been reported in association with central demyelinating syndromes including transverse myelitis. The signs and symptoms of the two syndromes may mimic one another and should always be considered in the differential diagnosis. Thus, careful investigation and a high index of suspicion are necessary to thoroughly exclude the coexistence of peripheral and central demyelination. When the conditions do co-occur, systemic inflammatory disease or infection should be considered and thoroughly investigated, as treatment must be directed toward any such underlying disease. In the rare case where no associated disease is identified, the treatment plan should independently consider recommendations for each demyelinating condition. Outcomes of AIDP versus central demyelinating syndromes vary considerably depending upon various prognostic factors, and it remains unclear how such prognosis translates to those cases with co-occurrence.