Compound Muscle Action Potential and Myosin-Loss Pathology in Patients With Critical Illness Myopathy: Correlation and Prognostication.

BACKGROUND AND OBJECTIVES: Prolonged compound muscle action potential (CMAP) duration and preferential loss of myosin are considered the diagnostic hallmarks of critical illness myopathy (CIM); however, their correlation and prognostic values have not been studied. We aimed to investigate the correlation between CMAP duration and myosin loss and their effect on mortality by comparing between patients with CIM with and without myosin loss. METHODS: We searched the Mayo Clinic Electromyography Laboratory databases (1986-2021) for patients diagnosed with CIM on the basis of prolonged distal CMAP durations (>15 msec in fibular motor nerve studies recording over the tibialis anterior or >8 msec in other motor nerves) and needle EMG findings compatible with myopathy. Electrodiagnostic studies were generally performed within 24 hours after weakness became noticeable. We included only patients who underwent muscle biopsy. Clinical, electrophysiologic, and myopathologic data were reviewed. We conducted myosin/actin ratio analysis when muscle tissue was available. We used the Fisher exact test for categorical data comparisons and the Mann-Whitney 2-tailed test for continuous data. We applied the Kaplan-Meier technique to analyze survival rates. RESULTS: Twenty patients (13 female patients) were identified [median age at diagnosis of 62.5 years (range: 19-80 years)]. The median onset of weakness was 24 days (range: 1-128) from the first day of intensive care unit admission. Muscle biopsy showed myosin loss in 14 patients, 9 of whom had >50% of myofibers affected (high grade). Type 2 fiber atrophy was observed in 19 patients, 13 of whom also had myosin loss. Patients with myosin loss had higher frequency of steroid exposure (14 vs 3; p = 0.004); higher median number of necrotic fibers per low-power field (2.5 vs 1, p = 0.04); and longer median CMAP duration (msec) of fibular (13.4 vs 8.75, p = 0.02), tibial (10 vs 7.8, p = 0.01), and ulnar (11.1 vs 7.95, p = 0.002) nerves compared with those without. Only patients with high-grade myosin loss had reduced myosin/actin ratios (<1.7). Ten patients died during median follow-up of 3 months. The mortality rate was similar between patients with and without myosin loss. Patients with high-grade myosin loss had a lower overall survival rate than those with low-grade or no myosin loss, but this was not statistically significant (p = 0.05). DISCUSSION: Myosin loss occurred in 70% of the patients with CIM with prolonged CMAP duration. Longer CMAP duration predicts myosin-loss pathology. The extent of myosin loss marginally correlates with the mortality rate. Our findings highlight the potential prognostic values of CMAP duration and myosin loss severity in predicting disease outcome.

Etiologies and Utility of Diagnostic Tests in Trigeminal Neuropathy.

OBJECTIVE: To evaluate the utility of diagnostic studies in identifying treatable etiologies of trigeminal neuropathy (TNP). PATIENTS AND METHODS: We performed a review of consecutive patients with nontraumatic, noniatrogenic TNP seen at Mayo Clinic between January 1, 2000, and August 31, 2019. Patients were excluded if they had trigeminal neuralgia without neuropathy or if their diagnostic work-up had been completed elsewhere. Data were analyzed to determine which diagnostic studies were most useful in identifying treatable etiologies. RESULTS: In total, 439 patients were included. The mean ± SD age was 56.3±13.6 years and 285 (64.9%) were female. Among the 180 cases in which an etiology was identified (41.0%), neoplasms were causative in 76 (42.2%), while specific connective tissue diseases were implicated in 71 (39.4%). Bilateral TNP (n=83) was associated with the presence of underlying connective tissue disease (P<.01). Identification of etiology was made by magnetic resonance imaging in 88 cases (48.8%), by abnormal connective tissue disease cascades combined with rheumatology consultation in 42 (23.3%), by a previously known connective tissue disorder in 30 (16.7%), and by abnormal connective tissue disease cascades alone in 8 (4.4%). Among the 439 study patients, electromyography was performed in 211 (48.1%) and lumbar puncture in 139 (31.7%), but their diagnostic utility was low. CONCLUSION: Underlying causes of nontraumatic, noniatrogenic TNP can be identified in approximately 40% of cases. Bilateral TNP is strongly associated with underlying connective tissue disease. Careful history taking, dedicated magnetic resonance imaging, and connective tissue panels have the greatest diagnostic utility. Electromyography and cerebrospinal fluid analysis are unlikely to elucidate treatable etiologies of TNP.

A Case Report of "Propofol Frenzy": Anesthetic Considerations for a Severe Propofol-Induced Neuroexcitation Reaction.

Propofol "frenzy" is considered a severe propofol-induced neuroexcitatory reaction involving nonepileptic spells of extremity thrashing, marked agitation, irregular eye movements, and impaired consciousness. Patients with propofol neuroexcitation present unique challenges for anesthesia providers due to underrecognition, lack of diagnostic tests, and differentiating from other comparable disorders that require medications that can exacerbate symptoms. We present a case of a healthy young patient whose postoperative course was complicated by propofol frenzy and functional limb paralysis following hip surgery with a spinal anesthetic and propofol sedation. This case highlights anesthesia considerations for propofol frenzy and discusses dexmedetomidine as a promising modality for prompt management.

Use of diffusion-weighted imaging to distinguish seizure-related change from limbic encephalitis.

OBJECTIVE: To determine whether diffusion-weighted imaging (DWI) can help differentiate peri-ictal signal abnormality from limbic encephalitis (LE) among patients with medial temporal lobe T2-hyperintensity. METHODS: We retrospectively identified patients with peri-ictal medial temporal lobe T2-hyperintensity using a Mayo Clinic database, and reviewed their DWI to look for unique diffusion restriction patterns. We then identified patients with medial temporal lobe T2-hyperintensity and LE, and reviewed their DWI to see if these patterns were ever present. Presence of diffusion restriction patterns was confirmed by a blinded neuro-radiologist. RESULTS: We identified 10 patients without LE who had peri-ictal unilateral medial temporal lobe T2-hyperintensity, ipsilateral to focal seizure onset. Nine of 10 (90%) had at least one of two diffusion restriction patterns potentially unique to seizure activity; four had gyriform hippocampal diffusion restriction ("Pattern 1"), three had diffuse hippocampal diffusion restriction that spared the most medial temporal lobe structures ("Pattern 2"), and two had both diffusion restriction patterns. The median patient age was 62 years (range 2-76 years) and 3/9 (33%) were female. In comparison, among patients with medial temporal lobe T2-hyperintensity and LE, only 5/57 (9%) had one of the diffusion restriction patterns ("Pattern 2") identified (P < 0.0001); all five had seizures reported. CONCLUSIONS: In patients with medial temporal lobe T2-hyperintensity and one of the diffusion restriction patterns described herein, the signal abnormality may be a peri-ictal phenomenon rather than indicative of LE and should prompt investigation for seizure. Even in patients with LE, these patterns should raise concern for seizure.

Chemical meningitis: a rare presentation of Rathke's cleft cyst.

Rathke's cleft cysts (RCC) are usually benign, sellar and/or suprasellar lesions originating from the remnants of Rathke's pouch. Rarely, RCC can present with chemical meningitis, sellar abscess, lymphocytic hypophysitis, or intracystic hemorrhage. We describe an unusual presentation of RCC in which the patient presented with a clinical picture of chemical meningitis consisting of meningeal irritation, inflammatory cerebrospinal fluid profile, and enhancing pituitary and hypothalamic lesions, in addition to involvement of the optic tracts and optic nerve.

Amyloid-ß-related angiitis presenting as a uveomeningeal syndrome.

A 59-year-old man had a 2-month history of nonfluctuating encephalopathy. He initially presented acutely with fevers, headaches, and word-finding difficulties. The sedimentation rate was elevated with a bland CSF and normal MRI head. Body CT showed diffuse pulmonary interstitial thickening with patchy opacification. Following treatment for pneumonia, there was resolution of fevers. No infectious etiology was identified. Within days of discharge, he developed bilateral uveitis, which was successfully treated with corticosteroid eyedrops and oral acyclovir. One month later, he developed confusion and unsteadiness. Repeat MRI was reportedly normal; body CT showed resolution of lung changes but diffuse lymphadenopathy persisted. A lymph node biopsy, reviewed at our institution, showed nonspecific reactive changes and fibrosis. Due to progressive encephalopathy and worsening headaches 2 months after symptom onset, the patient presented to our institution. On examination, he scored 30/38 on the Kokmen short test of mental status,(1) losing points for attention and immediate and delayed recall. Funduscopy revealed bilateral disc edema. He had mild appendicular ataxia and impaired tandem walk. The remainder of the examination was normal.