Neck extensor weakness resulting in dropped head is more often a part of a generalized neuromuscular disorder such as MG, ALS, or polymyositis. The term “dropped head syndrome” (isolated neck extension myopathy) usually refers to a condition characterized by severe weakness of the neck extensors in the absence of a generalized neuromuscular disorder and may be due to a restricted noninflammatory myopathy.1,2⇓ In such a case, there may, in fact, be additional weakness affecting periscapular, shoulder, and thoracic muscles or even more extensive distribution of weakness—“dropped head plus syndrome.”3 Hypothyroidism is often accompanied by a myopathy with proximal distribution.4 In 1880, William M. Ord described a woman with myxedema who had, among many other symptoms, head drop.5 There are, to our knowledge, no reports in the literature on isolated neck extensor weakness caused by hypothyroidism. We report a case of hypothyroidism presenting as an isolated dropped head syndrome, which subsided almost completely during treatment with levothyroxine.
Case report.
A 53-year-old man presented with a 4-year history of slowly progressive neck weakness and pain in the neck. He had “head drop” while sitting and standing and had noticed that his posterior neck muscles had increased in volume. For 6 months, he had also experienced a slight weakness in the arms and legs. His local neurologist had assessed the condition as a focal dystonia (antecollis), but injections of botulinum toxin in the sternocleidomastoid muscles were not successful. On examination in our department, there was a pronounced weakness of the neck extensors, resulting in a head drop. A prominent hypertrophy of the neck extensors was also noted. There was no limb weakness, and except for the findings described above, neurologic examination was normal. There was no palpable enlargement of the thyroid. Creatine kinase (CK) level was 4800 U/L (normal <270 U/L) and myoglobin level was 307 μg/L (normal <60 μg/L). Thyroid-stimulating hormone (TSH) level was 448 mU/L (normal 0.3 to 4.0 mU/L). T3 level was 0.51 pmol/L (normal 1.2 to 2.8 pmol/L) and T4 3.0 pmol/L (normal 9 to 21 pmol/L). Rheumatoid factor was 35 (normal <20). All other blood tests including thyroid peroxidase antibodies were normal. Needle electromyography (EMG) showed small polyphasic motor units in the neck extensors as well as in the limbs. A biopsy of the deltoid muscle was performed. Frozen sections were stained with hematoxylin and eosin, periodic acid–Schiff, oil red, van Gieson, and Gomori methods. In addition, sections were stained for ATPase activity at pH 4.6 and 9.4 and for NADH and cytochrome oxidase. Electron microscopy was also performed. The biopsy revealed marked fiber size variability (25 to 70 μm) of both type 1 and type 2 fibers, increased number of internal nuclei (occurring in ∼30% of the fibers), and early necrosis of a few fibers (figure 1A). There was no evidence of inflammation, no signs of mitochondrial myopathy, and no grouping of muscle fiber types. MRI of the neck showed increased volume (maximally 18 mm thick and 72 mm wide) of the splenius capitis muscle on both sides (figure 1B). EKG showed a first-degree atrioventricular block, but echocardiography revealed no abnormalities.
Figure. (A) Muscle biopsy showing marked fiber size variability of both type 1 and type 2 fibers, increased number of internal nuclei, and early necrosis of a few fibers. Hematoxylin and eosin stain. (B) Axial T1-weighted MRI of the neck at the level of C4. The splenius capitis muscle (arrow) on each side is disproportionately large compared with the other muscles. T2-weighted and fat-suppressed MRI did not show any pathologic signal change in the neck muscles.
Treatment was started with levothyroxine in gradually increased dosages up to 0.1 mg daily. On reexamination 4 months later, the patient was no longer aware of neck weakness and his neck pain had decreased considerably. He held his head in a normal position. There was only a minimal, hardly detectable weakness of neck extension, and the hypertrophy of the neck extensors had subsided. The CK level had decreased to 840 U/L and myoglobin to 123 μg/L. T4 level was 7.0 pmol/L and TSH 21 mU/L.
Discussion.
The dropped head syndrome is a heterogenic condition with different etiologies, as exemplified above. Some patients might respond to immunosuppressant treatment, as illustrated by a recent case report.3 The current case illustrates that hypothyroidism is another treatable cause of this syndrome. Weakness and hypertrophy of the neck extensors were the only clinical signs in our patient, even if it was evident from the results of the EMG and the muscle biopsy that the myopathy was more widespread. An overt myopathy has been reported rarely as an isolated clinical presentation of hypothyroidism,4 as in our patient, who lacked the classic symptoms of hypothyroidism such as lethargy, chilliness, constipation, and bradycardia. The abnormal thyroid function tests, the resolution both of these abnormalities and the dropped head with thyroid treatment, together with the fact that the degenerative disease emerged during a 4-year period render hypothyroidism the most likely cause for this dropped head syndrome. It is always important to consider MG in a patient with neck weakness. Hypertrophy of the neck muscles has, to our knowledge, not been described in MG. Because of the prominent muscle hypertrophy, the absence of strength fluctuations on clinical examination, and the clear-cut myopathic changes on EMG and in the muscle biopsy, MG was an unlikely diagnosis in this case. The prominent hypertrophy of the neck extensor muscles is a sign that we have not seen in other patients with the dropped head syndrome. In an anatomic study,6 the splenius capitis muscle has been reported to be on average 6.7 (3 to 14) mm thick and 51.5 (31 to 72) mm wide, which is smaller than in our patient. Affected muscles in hypothyroid myopathy may be enlarged, but it is uncertain if the basis is increased number of muscle fibers, increased size of muscle fibers, or increased amount of connective tissue.7
We have not been able to find any description in the literature of MRI of muscle in hypothyroid myopathy. It is interesting that edema-like alterations in the paraspinal muscles on MRI have been described in patients with the dropped head syndrome not associated with hypothyroidism.2 We have not seen any comments on thyroid function in the reports in the literature on neck extensor myopathy, but presumably thyroid function tests have been done with normal outcome. This case illustrates the importance of evaluating thyroid function in every case of myopathy of uncertain origin, even if clinically it seems to be restricted to the neck.
Footnotes
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Copyright © 2000 by AAN Enterprises, Inc.
- Received December 21, 1999.
- Accepted May 2, 2000.
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