Isolated abducens nerve palsy in a patient with asymptomatic SARS-CoV-2 infection.

The neuro-ophthalmological complications of SARS-CoV-2 infection are emerging but the spectrum of presentations and pathophysiological mechanism underpinning the association remains to be fully determined. We describe the case of a 44-year-old female who presented with a 12-hour history of diplopia preceded by a mild headache and found to have an isolated right abducens nerve palsy. Initial vital signs were normal but she developed a fever and nasopharyngeal swab confirmed SARS-CoV-2 infection by RT-PCR. All other investigations returned normal including blood tests, chest X-ray, MRI brain and cerebrospinal fluid analysis. She remained systemically well, and there was complete resolution of the abducens palsy and diplopia at two week follow up. In the absence of an alternative underlying cause or risk factors identified, the aetiology was presumed to be microvascular and potentially related to the viral infection. We add to the evolving literature of neuro-ophthalmological associations of SARS-CoV-2, discuss possible causal mechanisms and suggest considering asymptomatic SARS-CoV-2 infection in cases of isolated abducens palsy without clear risk factors.

Delayed diagnosis of spinal cord injuries in Huntington's disease.

Huntington's disease is a neurodegenerative disorder, characterised by progressive cognitive, motor and psychiatric symptoms. Patients with advanced disease presenting to emergency medical services can pose a diagnostic and management challenge for physicians unfamiliar with the condition. We describe two patients with Huntington's disease in whom the diagnosis of traumatic spinal cord injury was delayed, discuss the role that cognitive bias and other factors played in this delay, and the lessons we can learn.

Cell proliferation, movement and differentiation during maintenance of the adult mouse adrenal cortex.

Appropriate maintenance and regeneration of adult endocrine organs is important in both normal physiology and disease. We investigated cell proliferation, movement and differentiation in the adult mouse adrenal cortex, using different 5-bromo-2'-deoxyuridine (BrdU) labelling regimens and immunostaining for phenotypic steroidogenic cell markers. Pulse-labelling showed that cell division was largely confined to the outer cortex, with most cells moving inwards towards the medulla at around 13-20 µm per day, though a distinct labelled cell population remained in the outer 10% of the cortex. Pulse-chase-labelling coupled with phenotypic immunostaining showed that, unlike cells in the inner cortex, most BrdU-positive outer cortical cells did not express steroidogenic markers, while co-staining for BrdU and Ki67 revealed that some outer cortical BrdU-positive cells were induced to proliferate following acute adrenocorticotropic hormone (ACTH) treatment. Extended pulse-chase-labelling identified cells in the outer cortex which retained BrdU label for up to 18-23 weeks. Together, these observations are consistent with the location of both slow-cycling stem/progenitor and transiently amplifying cell populations in the outer cortex. Understanding the relationships between these distinct adrenocortical cell populations will be crucial to clarify mechanisms underpinning adrenocortical maintenance and long-term adaptation to pathophysiological states.