HIV peripheral neuropathy-related degeneration of white matter tracts to sensorimotor cortex.

Human immunodeficiency virus-associated distal sensory polyneuropathy (HIV-DSP) affects up to 50% of people with HIV and is associated with depression, unemployment, and generally worsened quality of life. Previous work on the cortical mechanism of HIV neuropathy found decreased gray matter volume in the bilateral midbrain, thalamus, and posterior cingulate cortex, but structural connectivity in this context remains under-studied. Here we examine alterations in white matter microstructure using diffusion imaging, hypothesizing that cortical white matter degeneration would be observed in continuation of the peripheral white matter atrophy previously observed in HIV-DSP. Male HIV seropositive patients (n = 57) experiencing varying degrees of HIV neuropathy underwent single-shell diffusion tensor imaging with 51 sampling directions. The scans were pooled using tractography and connectometry to create a quantitative map of white matter tract integrity, measured in generalized fractional anisotropy (GFA). The relationship between GFA and neuropathy severity was evaluated with linear regression. Correction for multiple comparisons was done using false discovery rate (FDR), a statistical method commonly used in genomics and imaging to minimize false positives when thousands of individual comparisons are made. Neuropathy severity was associated with decreased GFA along thalamocortical radiations leading along the lateral thalamus to sensorimotor cortex, with r = -0.405 (p < 0.001; FDR), as well as with the superior bilateral cingulum (r = -0.346 (p < 0.05; FDR)). Among a population of HIV neuropathy patients, greater neuropathy severity was correlated with lower white matter integrity running from midbrain to somatosensory cortex. This suggests ascending deafferentation extending from damaged peripheral nerves further downstream than seen previously, into the axons of third-order neurons. There is also evidence of cingulum degeneration, implying some more complex mechanism beyond the ascending atrophy observed here.

Distal neuropathic pain in HIV is associated with functional connectivity patterns in default mode and salience networks.

HIV-associated distal neuropathic pain (DNP) is one of the most prevalent, disabling, and treatment-resistant complications of HIV, but its biological underpinnings are incompletely understood. While data specific to mechanisms underlying HIV DNP are scarce, functional neuroimaging of chronic pain more broadly implicates the role of altered resting-state functional connectivity within and between salience network (SN) and default mode network (DMN) regions. However, it remains unclear the extent to which HIV DNP is associated with similar alterations in connectivity. The current study aimed to bridge this gap in the literature through examination of resting-state functional connectivity patterns within SN and DMN regions among people with HIV (PWH) with and without DNP. Resting state functional magnetic resonance imaging (rs-fMRI) scans were completed among 62 PWH with HIV-associated peripheral neuropathy, of whom 27 reported current DNP and 35 did not. Using subgrouping group iterative multiple estimation, we compared connectivity patterns in those with current DNP to those without. We observed weaker connectivity between the medial prefrontal cortex (MPFC) and posterior cingulate cortex (PCC) and stronger connectivity between the anterior cingulate cortex (ACC) and thalamus among those reporting DNP. Overall, these findings implicate altered within DMN (i.e., MPFC-PCC) and within SN (i.e., ACC-thalamus) connectivity as potential manifestations of adaptation to pain from neuropathy and/or mechanisms underlying the development/maintenance of DNP. Findings are discussed in the context of differential brain response to pain (i.e., mind wandering, pain aversion, pain facilitation/inhibition) and therapeutic implications.

Superior chronic tolerability of adjunctive modafinil compared to pramipexole in treatment-resistant bipolar disorder.

BACKGROUND: Suboptimal outcomes are common in bipolar disorder (BD) pharmacotherapy, and may be mitigated with novel adjunctive agents such as modafinil (a low-affinity dopamine transport inhibitor) and pramipexole (a dopamine D2/D3 receptor agonist). While uncontrolled long-term effectiveness data have been reported for these treatments, reports specifically assessing their comparative acute versus chronic tolerability in BD are lacking. Such information, particularly in relation to discontinuation causes, has substantial relevance, providing initial indications to clinicians which treatment may be better tolerated, and to researchers which agent ought to be assessed in longer-term controlled trials. METHODS: BD outpatients assessed with the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD) Affective Disorders Evaluation, and followed with the STEP-BD Clinical Monitoring Form, were naturalistically prescribed adjunctive modafinil or pramipexole, and somatic/psychiatric intolerability discontinuation rates were compared. RESULTS: Among 63 BD outpatients (mean ± SD age 43.5 ± 14.3 years, 60.3% female, 42.9% type I, 44.4% type II, 12.7% type not otherwise specified), taking 3.5 ± 1.5 (median 3) concurrent prescription psychotropics, adjunctive modafinil (n=24) for 626.9 ± 863.9 (286) days versus pramipexole (n=39) for 473.7 ± 613.4 (214; p=0.51) days yielded a 26.0% lower somatic/psychiatric intolerability discontinuation rate (12.5% vs. 38.5%; p<0.05), with most of the difference accounted for by more pramipexole somatic intolerability discontinuations, due to nausea and sedation, after the first 12 weeks of treatment. LIMITATIONS: No placebo comparison group. Small sample of predominantly female Caucasian insured outpatients, taking complex concurrent medication regimens. CONCLUSIONS: Further studies are warranted to assess our preliminary observation that modafinil, compared to pramipexole, may be better tolerated for longer-term BD treatment.