Conditions with acute-on-chronic compromise potentially presenting to ICU with no previous diagnosis
| Condition | Clues |
| Motor neurone disease | Combination of upper and lower motor neurone signs Progressive worsening No sensory findings Bilateral tongue wasting, ‘split hand’—wasted first dorsal interosseus and abductor pollicis brevis Fasciculation |
| Acid maltase deficiency (adult Pompe’s disease) | Paraspinal muscle wasting Pelvic girdle weakness, particularly of hip flexion EMG fibrillation and myotonic discharges in iliopsoas and thoracic paraspinal muscles Diagnosis—send dried blood spot enzyme assay for α-glucosidase Enzyme replacement therapy available |
| Myotonic dystrophy (DM1) | Reduced respiratory drive Weak respiratory muscles Postoperative complications in 10% (respiratory depression or pneumonia) may require ICU admission Frontal balding (most marked in men) Temporalis muscle atrophy Cataracts and ptosis Weakness of facial and neck flexion muscles Distal forearm wasting, weak hand grip and foot drop Smooth muscle involvement
Thenar eminence percussion elicits an exaggerated contraction with delayed relaxation (myotonia) Electromyography identifies myotonia |
| Mitochondrial myopathy Genes potentially in either mitochondrial DNA (mtDNA) or nuclear DNA
| Ptosis, progressive external ophthalmoplegia, optic atrophy or pigmentary retinopathy, cataract Sensorineural hearing loss Endocrine—diabetes, exocrine pancreatic failure, primary and secondary gonadal failure Low body mass index (‘thin, diabetic and deaf’ and often young) Cardiac—heart block, cardiomyopathy Gastrointestinal dysmotility Multiple neck lipomatosis (MERRF) Myoclonus and epilepsy, particularly occipital seizures in a young adult or epilepsia partialis continua Neuropathy, ataxia Psychiatric, developmental delay or cognitive decline Hirsutism occasionally (mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes) Ventilatory muscle weakness and reduced respiratory drive—hypoventilation following sedation or infection (see figure 12). Beware propofol (and valproate) use |
| Myofibrillar myopathies | Common histopathological pattern but has many genetic causes Onset usually 25–45 years Distal, proximal or scapuloperoneal Potential facial and pharyngeal weakness Cardiomyopathy and/or peripheral neuropathy Potential intestinal pseudo-obstruction Cataracts in αB crystalline-related myofibrillar myopathies Serum creatine kinase normal or mildly elevated |
| Some congenital myopathies (always consider congenital myasthenia in these patients) | Tall, with a thin face and high-arched palate Pes cavus, hammer toes Generalised weakness and atrophy Serum creatine kinase<3 times upper limit Some have prominent respiratory muscle weakness while still ambulant (eg, mutations in TPM3 or SEPN1). Congenital myasthenia, can present in adults Slow channel—weakness in cervical muscles and finger extensors; mild ophthalmoparesis. Repetitive compound muscle action potential on motor studies neurophysiologically DOK7—long myopathic face, myasthenic snarl, often a wasted tongue, mild proximal limb weakness, ptosis but no ophthalmoplegia RAPSYN—frequent admissions to ICU with respiratory failure following infection, high-arched palate and long ‘myopathic face’, little ophthalmoplegia but often a squint. Mutation in the epsilon subunit of the acetylcholine receptor causes significant ophthalmoplegia—often stable, most common cause in UK |
GABAA, gamma-aminobutyric acid-A; ICU, intensive care unit; MERRF, myoclonus epilepsy with ragged-red fibers; MOG, myelin oligodendrocyte glycoprotein; MRC, Medical Research Council.