We wish to describe a case of hypothyroidism presenting as isolated dropped head syndrome which reverted completely by 1 month following thyroxine replacement.
A 60-year-old man presented with difficulty in keeping his neck upright. He had experienced pain and discomfort in the back of his neck for the past 3 months. While walking, his neck without his knowledge assumed a flexed position which was pointed out by his friends. Later on, he had to lean back and support his neck on a wall to keep it erect. He had difficulty in swallowing food due to the head drop. Except for this complaint, he did not have any significant symptom. He did not have any limb weakness. On examination, he had a hoarse voice; his neck extensors were severely weak with preserved neck flexor power [Video 1]. He had normal power of his extremities and there was no fatiguability. Rest of the neurological examination was normal. His creatine kinase level was 590 (normal <20 U/L). His thyroid stimulating hormone level was 102 (normal: 0.5–4.5 mIU/L), T3 was 0.8 ng/ml (normal: 0.8–2.1 ng/ml), and T4 was 3.21 μg/ml (normal: 5–14.1 μg/ml). All other blood tests were normal. There was no decremental response on repetitive nerve stimulation. Electromyography (EMG) revealed myopathic potentials in cervical paraspinal muscles while rest of the muscles tested had normal EMG findings. The patient was not willing for further tests. He was started on thyroxine 100 μg daily. One month later, his neck power was found to be completely normal [Video 2].
”Dropped head syndrome” refers to severe weakness of neck extensors with normal or only mildly weak neck flexors. Causes for dropped head syndrome include myasthenia gravis, amyotrophic lateral sclerosis, polymyositis, hypothyroidism, adult-onset nemaline body myopathy, postpolio syndrome, chronic inflammatory demyelinating polyneuropathy, mitochondrial myopathy, Cushing's syndrome, and a distinct, benign disorder called isolated neck extensor myopathy., Except for a hoarse voice, our patient lacked the usual constitutional symptoms of hypothyroidism and did not have muscle weakness elsewhere. Similar cases have been reported earlier in literature and emphasize that hypothyroidism should be one of the most important differential diagnoses to be considered in a patient with dropped head syndrome.