Research highlights in Neurology and Neurosurgery — May 2020

Dec. 31, 2020

Mayo Clinic Neurology and Neurosurgery studies address the risk of carotid artery injury, clinical diagnosis of progressive supranuclear palsy and characterization of amphiphysin-IgG autoimmunity.

Avoiding carotid artery injury: Experience may be more important than technique

Transsphenoidal resection has evolved into the standard of care for most pituitary adenoma operations. Recently, the endoscopic endonasal approach has gained popularity as an alternative to microsurgery for transsphenoidal resection. Numerous studies attempting to assess the differential risk of internal carotid artery injury between the two techniques have had equivocal and contradictory results.

In the first systematic review comparing the two techniques in the modern era, Mayo Clinic researchers found that operator inexperience may be a more important risk factor than choice of surgical technique. The researchers performed a systematic literature review of publications from 2002 to 2017 that reported the outcomes of internal carotid artery injury in cases involving microsurgery or the endoscopic endonasal approach.

In an effort to look beyond the learning curve pertinent to the early adoption of surgical skills, the researchers focused on surgeries performed by operators whose experience included at least 250 cases. Within this population of highly experienced neurosurgeons, the researchers noted a dramatic decrease in the overall rate of cerebrovascular complications, with a consistently reproduced improvement in safety correlated with increasing operator experience. The researchers also observed a de facto parity between microsurgery and the endoscopic endonasal approach for transsphenoidal resection, with most highly experienced surgeons reporting a less than 0.5% incidence of internal carotid artery injury.

The researchers emphasize the need for consolidated care in pituitary centers of excellence, improvement of high-fidelity simulators, and skull base mentorship between senior and junior staff.

Perry A, et al. Beyond the learning curve: Comparison of microscopic and endoscopic incidences of internal carotid artery injury in a series of highly experienced operators. World Neurosurgery. 2019;131:e128.

Absence of orthostatic hypotension may distinguish PSP from other pathologies

The clinical diagnosis of progressive supranuclear palsy (PSP) can be challenging due to the variability of its phenotype and overlap with other parkinsonian disorders. Autonomic dysfunction has emerged as a frequent feature of atypical parkinsonisms; however, data on autonomic dysfunction in PSP, a tauopathy, have been inconsistent or contradictory. In a retrospective study, Mayo Clinic researchers found that the absence of orthostatic hypotension was the strongest autonomic parameter distinguishing autopsy-confirmed PSP from alpha-synuclein pathology.

The researchers reviewed the cases of 14 patients with PSP, 18 with multiple system atrophy and 24 with Lewy body disease. The reviews included the results of antemortem autonomic testing and clinical evaluations by Mayo Clinic movement disorder specialists, as well as postmortem examinations. Although multiple system atrophy and Lewy body disease were frequently associated with orthostatic hypotension, none of the patients with autopsy-confirmed PSP had orthostatic hypotension.

The researchers note that their data support the conclusion that the cardiovascular adrenergic system is relatively spared in PSP, as well as affirm the value of identifying orthostatic hypotension as a means of reaching an accurate diagnosis in a patient with atypical parkinsonism. The results also demonstrate the value of comprehensive autonomic testing to distinguish this class of neurodegenerative disorders.

van Gerpen JA, et al. Progressive supranuclear palsy is not associated with neurogenic orthostatic hypertension. Neurology. 2019;93:e1339.

Characterizing amphiphysin-IgG autoimmunity

Amphiphysin is an intracellular protein regulating synaptic vesicles. Amphiphysin-immunoglobulin G (IgG) autoimmunity was first recognized in stiff person syndrome with breast cancer. Brainstem, cerebellar and neuropathy presentations, as well as lung cancer, were subsequently described. Although reports indicate that neuropathy is the most common neurological presentation, detailed understanding of the amphiphysin-IgG-associated peripheral nervous system involvement is lacking.

Mayo Clinic researchers have found that amphiphysin-IgG autoimmune neuropathy has a recognizable phenotype, is frequently immune responsive and can prompt early diagnosis of breast cancer. The researchers reviewed the records of 53 Mayo Clinic patients with amphiphysin-IgG who were examined by indirect immunofluorescence and Western blot between 1995 and 2018. Among the 53 patients, 33 (60%) had neuropathy, including 21 patients with amphiphysin-IgG alone and 12 with coexisting autoantibodies.

The neuropathies in isolated amphiphysin-IgG autoimmunity included polyradiculoneuropathy, diffuse sensory neuronopathy and facial neuropathy with gastroparesis. Pain, breast cancer and central nervous system (CNS) involvements commonly coexisted with these neuropathies.

Neuropathy frequently prompted breast cancer diagnosis. Stiff person spectrum disorder was the most common CNS involvement. In contrast, patients with coexisting autoantibodies commonly had lung cancer.

Among all patients studied, 58% responded to immunotherapy. Patients with amphiphysin-IgG alone had more favorable immunotherapy responses than did patients with coexisting autoantibodies.

Dubey D, et al. Amphiphysin-IgG autoimmune neuropathy: A recognizable clinicopathologic syndrome. Neurology. 2019;93:e1873.