12.16. Paraspinous Myopathies
Dropped Head and Bent Spine Syndromes
- General features:
- Neck extensor weakness as an isolated symptom or predominant feature of neuromuscular disease is rare
- Similarly predominant thoracic or lumbar paraspinous muscle weakness to the extent of interfering with function is also rare in neuromuscular disorders
- Clinical features of isolated neck extensor myopathy (INEM):
- Presents in the seventh decade or older
- Difficulty in keeping the head erect; severely affected patients the chin rests on the chest
- May develop insidiously over several months or acutely over a week
- Often concomitant burning pain as it develops
- No other associated muscle weakness
- Dysphagia is a concomitant symptom (postural not due to intrinsic muscle weakness)
Isolated Trunk Extensor Myopathy (camptocormia; ITEM)
- Clinical Presentation:
- Affects elderly patients; women greater than men; 60% may have an affected relative
- Inability to stand erect due to thoracic and lumbar paraspinal muscle weakness
- Associated with INEM
- Insidious onset over 1–8 years
- Patients may have proximal weakness greater in the pelvis than shoulder girdle
- EMG:
- Focal paraspinous myopathy
- INEM:
- Positive sharp waves and fibrillation potentials
- Low amplitude short duration MUAPs
- ITEM:
- Myopathic changes of the paraspinal muscles
- Laboratory evaluation:
- Pathology (muscle biopsy):
- Atrophied muscles; fibrosis and edema
- Variation of fiber size; fiber spitting; increased internal nuclei
- Rare angular esterase-positive fibers are noted in INEM
- Differential diagnosis:
- MG (ptosis, ophthalmoparesis, weakness)
- ALS (fasciculations, fibrillation of the tongue, hyperreflexia)
- Spinal muscular atrophy (proximal > distal weakness; absent reflexes)
- Congenital myopathy (dysmorphisms, thin muscles)
- Inclusion body myopathy (swallowing dysfunction; contracture of forearm musculature)
- PM/DM complex (associated extensor rash; proximal > distal weakness; dysphagia)
- CIDP (distal > proximal weakness; large fiber sensory loss; absent reflexes)
- Severe cervical stenosis (decreased range of motion to all planes; inverted radial reflex; proximal muscle weakness)
- Prolonged chemodenervated from Botox injection
- Myotonic dystrophy (dysmorphism, myotonia, cataracts)
- Nemaline (tall, thin, dysmorphism)
- Mitochondrial myopathy (associated VIII nerve dysfunction, short stature, exercise intolerance, myoglobinuria)
- FSH dystrophy (severe lower face; humeral involvement)
- Carnitine deficiency (exercise intolerance myoglobinuria, cramps)
Rare Presentations of Isolated Trunk Extensor Myopathy
- Dropped head:
- Parkinson's Disease; akinetic rigid syndrome
- Bent spine:
- ALS
- Hypothyroid myopathy
- DM/polymyositis complex
Differential Diagnosis of Skeletal Abnormalities that Simulates Bent Spine Syndrome
- Torticollis
- Dystonia of chronic regional pain syndrome (CRPS)
- Ankylosing spondylitis
- Severe kyphosis/lordosis
- Ochronosis (homogentisic aciduria)
- Thoracic disc disease
|