A Man With a Dropped Head

A 64-year-old man developed weakness in his arms over 6 months. In the last 2 months, he noticed a tendency for his head to drop forward, and he had difficulty raising it when lying in bed. He also had mild difficulty swallowing.

Past medical history was remarkable for benign prostatic hypertrophy and mild hypertension.

Examination revealed normal mentation and cranial nerves. There was no tongue weakness, atrophy, or fasciculations. He had weakness of the neck extensors with a tendency for the neck to drop forward ( Fig. 31-1 ). There were no neck flexor contractions when lying in lateral decubitus suggestive of dystonia causing head flexion. He had flattening of the right shoulder from muscle atrophy. Neck flexion strength was 4/5, extension was 3−/5. Strength was 4+/5 in the left shoulder; 3/5 in the right shoulder; 4+/5 in both biceps; 5/5 in the triceps, wrist flexors, and extensors; and 3/5 in hand muscles. There was bilateral interossei muscle atrophy. Hip flexors and extensors were 4+/5; quadriceps, hamstrings, and distal leg muscles were 4/5. Reflexes were 3+ in the upper extremities and 2+ in the lower extremities with a right Babinski sign. Sensory examination and coordination were normal. There was no rigidity. Fasciculations were noted in the right shoulder and interossei muscles.

What is the Differential Diagnosis?

This patient presented with dropped head syndrome (DHS) caused by weakness of neck extensor muscles. DHS has many etiologies ( Table 31-1 ), and in patients with this presentation, one should always look for treatable causes, such as myasthenia gravis that is diagnosed with an edrophonium test ( Fig. 31-2 ), measurement of acetylcholine receptor antibody titers, and, if negative, muscle-specific protein kinase antibodies and repetitive stimulation tests. Polymyositis should be considered, for which the patient is checked for elevated serum creatine kinase (CK) and the characteristic EMG and muscle biopsy. Other reversible causes include endocrine disorders and electrolyte abnormalities.

Table 31-1

Conditions Associated With Cervical Paraspinal Muscle Weakness and Dropped Head Syndrome

From Narayanaswami P, Bertorini T. The dropped head syndrome. J Clin Neuromuscul Dis . 2000;2:106–112.

Prominent, early paraspinal weakness in generalized processes

Amyotrophic lateral sclerosis
Myasthenia gravis
Polymyositis/dermatomyositis

Isolated paraspinal muscle weakness

Isolated neck extensor myopathy
Bent spine syndrome
Benign focal amyotrophy

Other diseases associated with paraspinal weakness or atrophy, or both

Chronic inflammatory demyelinating polyneuropathy
Eaton–Lambert myasthenic syndrome
Inclusion body myositis
Facioscapulohumeral dystrophy
Nemaline myopathy
Proximal myotonic myopathy
Mitochondrial myopathy
Acid maltase deficiency
Carnitine deficiency
Hypokalemic myopathy
Hyperparathyroidism

Disorders that mimic dropped head syndrome

Cervical dystonia (anterocollis), Parkinson disease
Fixed skeletal deformities of the spine

Amyotrophic lateral sclerosis (ALS) is another cause of DHS, and this is diagnosed by the presence of tongue and limb weakness, fasciculations, and long tract signs. There is also evidence of diffuse denervation and fasciculations and decreased motor unit recruitment with normal nerve conduction tests on EMG.

The presence of a Babinski sign in this person with head drop and the interossei muscle atrophy is against the diagnosis of myasthenia and polymyositis. There were also some fasciculations in the shoulder and interossei, suggesting that he had ALS.

Laboratory studies included serum CK, T4, thyroid-stimulating hormone, B ₁₂ , and fluorescent antinuclear antibody titers. A complete metabolic panel was normal.

An EMG Test was Performed

Motor Nerve Studies

Nerve and Site	Latency (ms)	Amplitude (mV)	Conduction Velocity (m/s)
Median Nerve R.	Normal ≤ 4.2	Normal ≥ 6	Normal ≥ 50
Wrist	3.7	15	–
Elbow	8.3	15	53

Nerve and Site	Latency (ms)	Amplitude (mV)	Conduction Velocity (m/s)
Ulnar Nerve R.	Normal ≤ 3.6	Normal ≥ 8	Normal ≥ 50
Wrist	2.9	16	–
Below elbow	7.7	16	51
Above elbow	9.7	16	60

Nerve and Site	Latency (ms)	Amplitude (mV)	Conduction Velocity (m/s)
Peroneal Nerve R.	Normal ≤ 5.7	Normal ≥ 3	Normal ≥ 40
Ankle	4.9	8	–
Fibular head	10.9	8	48
Knee	12.3	7	43
Tibial Nerve R.	Normal ≤ 5.3	Normal ≥ 4	Normal ≥ 40
Ankle	3.4	16	–
Pop. fossa	11.9	13	45

F-Wave and Tibial H-Reflex Studies

Nerve	Latency (ms)	Normal Latency ≤ (ms)
Median nerve R.	27.2	30
Ulnar nerve R.	26.8	30
Peroneal nerve R.	53.0	54
Tibial nerve R.	51.2	54
H-reflex R.	33.8	34
H-reflex L.	33.4	34

Sensory Nerve Studies

Nerve	Onset Latency (ms)	Normal Onset Latency ≤ (ms)	Peak Latency (ms)	Normal Peak Latency ≤ (ms)	Amp (μV)	Normal Amp ≥ (μV)	Conduction Velocity (m/s)	Normal Conduction Velocity ≥ (m/s)
Median nerve R.	2.4	2.6	2.9	3.1	21	20	54	50
Ulnar nerve R.	2.2	2.6	2.7	3.1	13	13	55	50
Sural nerve R.	3.3	3.5	3.8	4.0	12	11	42	40

EMG Data

Muscle	Insrt Activity	Fibs	Pos Waves	Fasc	Amp	Dur	Poly	Pattern
Cervical paraspinals R.	Inc	None	None	Few	Dec	Brief	Many	Full
Tongue R.	Norm	None	None	None	Norm	Norm	None	Full
Infraspinatus R.	Norm	None	None	None	Norm	Norm	None	Full
Trapezius R.	Norm	None	None	None	Norm	Norm	None	Full
Deltoid R.	Inc	1+	1+	Few	Variable/Lg	Inc	Many	Red
Biceps brachii R.	Inc	1+	1+	Few	Variable/Lg	Inc	Many	Full
First dorsal interosseus R.	Inc	1+	1+	Few	Variable/Lg	Inc	None	Red
Thoracic paraspinal R.	Inc	1+	1+	Few	Norm	Norm	None	Full
Vastus lateralis R.	Inc	None	None	Few	Lg	Inc	None	Red
Tibialis anterior R.	Inc	None	1+	None	Lg	Inc	None	Red
Peroneus longus R.	Norm	None	None	Few	Lg	Inc	None	Full
Gastrocnemius R.	Inc	1+	1+	Few	Lg	Inc	None	Full