Early on, there is decreased recruitment and interference, with decreased motor unit action potential amplitudes. In 2-4 weeks, fibrillations will develop, with possible fasciculations. Over time, reinnervation will lead to polyphasic motor units.
Nerve conduction velocities and sensory studies are normal. Imaging:
Inflammation of the anterior spinal cord may be detected with MRI. Post-polio syndrome:
The diagnosis of PPS is by exclusion of other conditions and demonstration of progressive weakness over time.
Encephalitis caused by echovirus or coxsackie virus Meningitis
Guillain-Barre syndrome Motor polyneuropathies Acute transverse myelitis
Vaccination programs have tremendously decreased the incidence of poliomyelitis in developed countries. However, rare cases are still reported in countries with good vaccine programs, frequently in isolated cultures that reject modern medical care. In countries without adequate vaccination, poliomyelitis is still common.
Once a patient has poliomyelitis, the only treatment is supportive therapy. This includes physical therapy to prevent contractures and joint ankylosis, prosthetic devices, and respiratory/swallowing therapy to minimize pulmonary complications like aspiration and atelectasis. Some clinicians recommend that patients with PPS minimize their activity, but studies suggest that exercise is beneficial for PPS, too.
Respiratory failure can be caused by central depression, weakness of the respiratory muscles, or other complications (pneumonia, edema, etc.) associated with airway obstruction. Cardiovascular collapse may also occur from infection of the brainstem. These situations require intensive care with artificial ventilation.
During the acute phase of polio paralysis, the mortality rate is fairly low (5-10%). Patients requiring ventilation during this period usually recover over a period of several months, during which the respiratory muscles become reinnervated and hypertrophic. Continued dependence on artificial ventilation is uncommon. In general, the prognosis for polio patients is good. Patients that later develop PPS will experience slowly worsening weakness. This does not usually cause increased disability or mortality, although deterioration of respiratory function is a rare possibility.
Dalakas MC (1995) The post-polio syndrome as an evolved clinical entity. Definition and clinical description. Annals of the New York Academy of Science 753: 68-80 Mulder DW (1995) Clinical observations on acute poliomyelitis. Annals of the New York Academy of Science 753: 1-10
Price RW, Plum F (1978) Poliomyelitis. In: Handbook of clinical neurology, vol. 32, pp 2091-2092
Rowland LP (2000) Viral infections of the nervous system: syndrome of acute anterior poliomyelitis. In: Merritt's neurology, 10th edn. pp 764-767
Trojan DA, et al (1994) Predictive factors for post-poliomyelitis syndrome. Arch Phys Med Rehab 75: 770-777
Bulbospinal muscular atrophy (Kennedy's syndrome)
Bulbospinal muscular atrophy (BSMA), or Kennedy's syndrome, affects the Anatomy lower (alpha) motor neurons found in the brainstem cranial nerve motor nuclei and the anterior horns of the spinal cord. On autopsy, patients with BSMA show mild atrophy of the brainstem and spinal cord. Muscle atrophy is also present, with signs of denervation and reinnervation.
The mean onset for BSMA is 30 years (range, 15-60 years). Patients exhibit Symptoms symmetrical weakness that progresses slowly over many years, and typically do not need canes or walkers until they are in their fifties or sixties. Facial, tongue, and proximal weakness are typical at presentation. Dysphagia, dysarthria, and masseter weakness are commonly observed.
As BSMA only affects lower motor neurons, there are no upper motor neuron Signs signs. Tendon reflexes are reduced or absent. Fasciculations are common in the face (Fig. 5B). Vibratory sensation may be reduced, and patients often show a mild postural tremor. Gynecomastia occurs in 50% of patients (Fig. 5A).
BSMA is an X-l inked recessive disorder, caused by a tri-nucleotide repeat Pathogenesis expansion in the first exon of the androgen receptor gene on chromosome Xq11-12. It is unknown how disruption of the androgen receptor in this way leads to specific loss of lower motor neurons, as there are other mutations in this gene that cause testicular feminization but have no affects on motor neurons.
Diagnosis Genetic: Patients with appropriate signs and symptoms are diagnosed by positive genetic testing.
Laboratory: As muscles are chronically denervated, creatine kinase levels are elevated (up to 10-fold). A muscle biopsy is frequently performed and shows evidence of denervation.
EMG: Chronic denervation is also demonstrated by EMG.
Differential diagnosis Therapy
ALS: BSMA has no upper motor neuron signs, distinguishing it from ALS.
Currently, the only treatment is supportive care when the muscle weakness becomes problematic.
The number of CAG repeats present in the gene directly correlates with the age of onset and severity of the disease (i.e., more repeats means an earlier onset and greater severity.)
Dubovitz V (1995) Disorders of the lower motor neurons: the spinal muscular atrophies. In: Muscle disorders in childhood, 2nd edn. Saunders, London, pp 325-369 Wang CH, Carter TA, Gilliam TC (1997) Molecular and genetic basis of the spinal muscular atrophies. In: Rosenberg RN, Pruisner SB, DiMauro S, Barchi RL (eds) The molecular and genetic basis of neurological disease, 2nd edn. Butterworth-Heinemann, Boston, pp 787796
General disease finder
This overview will help to find neuromuscular disease patterns in the different sections
Cushing's disease: steroid myopathy Adrenal dysfunction
Addison's disease: general muscle weakness
Periodic paralysis Aldosteronism
CN: VII AIDS
Polyneuropathies: inflammatory, immune mediated, treatment related Myopathies: inflammatory, treatment related Neoplastic: Lymphoma (direct invasion)
Treatment related: polyneuropathy/myopathy Ddl, ddC, Foscarnet, Isoniazid Zidovudine
Polyneuropathy (distal, rarely proximal, rare ulcers) Alcoholism
Mononeuropathy-radial nerve (compression)
Acute necrotizing myopathy and myoglobinuria Chronic proximal weakness Hypokalemic paralysis Myoglobinuria
Compartment syndromes (prolonged compression)
Familial amyloid polyneuropathies Amyloid
Sensorimotor neuropathy Autonomic involvement
Polyneuropathy, painful, hearing loss
Gelsolin type V, VII and other CN Mild polyneuropathy Primary amyloidosis (AL)
Deposition of immunoglobulin light chains in tissue
Painful neuropathy Autonomic involvement Carpal tunnel syndrome Muscle amyloid Amyloidoma (trigeminal root)
Secondary or reactive amyloidosis (AA)
Chronic inflammatory diseases, rheumatoid diseases, osteomyelitis Deposition of acute phase plasma protein, serum amyloid A: polyneuropathy not significant
Anemia Cobalamin deficiency, vitamin B12 polyneuropathy
Anesthesia Regional: Epidural or spinal anesthesia may cause cauda equina lesions
Lower extremity (30%): Mononeuropathies of peroneal, sciatic, or femoral nerves
Neuromuscular transmission disorders induced by muscle relaxants
Axillary or femoral artery puncture (brachial plexus and femoral nerve) Brachial artery: median nerve
Cerebral angiography: femoral nerve lesions
Acute ICU steroid myopathy (status asthmaticus) Steroid myopathy
Entrapment neuropathies and compression (ulnar, peroneal nerves) Churg Strauss syndrome
Hearing loss: Refsum's disease, Cockayne Syndrome, mitochondrial disorders, vasculitis, some types of amyloidosis and hereditary neuropathies
Bone marrow transplantation
Inflammatory myopathies MG
Facial nerve lower branch Carotid surgery
Hypoglossal nerve Vagal recurrent nerve
Cranial nerves (meningeal carcinomatosis, base of the skull metastasis) Cancer
Mononeuropathies (pressure, toxic, following operations)
Radiculopathies (meningeal carcinomatosis, compression or infiltration of roots, multiple spinal metastasis), cauda equina syndrome
Polyneuropathies (treatment related and paraneoplastic, rarely infiltrative)
Myopathies: cachexia, dermatomyositis/polymyositis, necrotizing, neuromyo-
Neuromuscular transmission: MG and thymoma, LEMS and (lung) cancer
Antineoplastic treatment associated polyneuropathy:
Cisplatinum (Carboplatin, Oxaliplatin)
Plexopathies (brachial, lumbar, sacral)
Paraneoplastic disease Cranial nerve: Optic nerve Polyneuropathies (all types) LEMS
Muscle: inflammatory and necrotizing myopathies
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