A 37-year-old chef was referred to a neurologist with progressive wasting and weakness of the right hand.
He had had the problem for several months and had noticed reduced dexterity and clumsiness using the hand whilst at work. In addition he had burnt his hands whilst cooking or smoking, and has been completely unaware of doing so. This had caused multiple sores over the fingertips of both hands; otherwise he has been well in himself. He had no known medical history, however did sustain a whiplash injury in a recent minor car accident.
He took no regular medication, smoked 30 cigarettes per day and had no family history of medical problems.
On examination he appeared well in himself. He had a right Horner’s syndrome, however the rest of the cranial nerve examination was normal.
On examination of the upper limb, there was evidence of right dorsal interossei, hypothenar eminence, adductor pollicis brevis and forearm wasting. There were also multiple scars found over the fingertips of both hands. Tone was asymmetrically depressed at the wrist and elbow bilaterally (R>L) and reflexes were bilaterally depressed.
On examination of power, handgrip and wrist flexion/extension were asymmetrically weak (right>left). Upper body strength appeared normal.
There was no cerebellar dysfunction; however examination of sensation revealed reduced pain and temperature sensation affecting both arms and anterior/posterior chest wall.
Lower limb examination revealed increased tone symmetrically with pathologically brisk reflexes and extensor plantar responses bilaterally. Power, co-ordination and sensation were normal.
Chest examination was normal.
Full blood count and biochemical profile Normal
Chest x ray Normal
Cervical spine x ray Normal
In light of the history and investigations so far, what is the likely diagnosis for this patient?
Anterior spinal artery infarct
Cervical myelopathy
Distal spinal muscular atrophy
Syringomyelia - Correct
Thoracic inlet syndrome
Explanation:
This patient presents with wasting and weakness of the hands, dissociated sensory disturbance with painless burns in the upper limb, and pyramidal signs in the lower limbs.
These findings would all be in keeping with a diagnosis of syringomyelia affecting the cervical cord.
There is sympathetic involvement as the patient has a right Horner’s syndrome.
The syrinx does not extend to involve the brainstem, as there is no cranial nerve dysfunction involving cranial nerves V, VII, IX and X.
A magnetic resonance imaging (MRI) scan is required to visualise the lesion and neurosurgical opinion. Treatment options include syringoperitoneal shunt or direct drainage of the syrinx into the subarachnoid space.
Anterior spinal artery infarct would have resulted in an acute anterior cord syndrome with pyramidal signs and dissociated sensory disturbance affecting the legs and lower motor neurone (LMN) signs at the level of the infarct (T4-T6 watershed).
Distal spinal muscular atrophy can resemble amyotrophic lateral sclerosis but is limited to pure lower motor neurone degeneration. This condition would not explain the prominent sensory disturbance and the Horner’s syndrome.
Thoracic inlet syndrome involving the lower brachial plexus would cause a C8/T1 sensory and motor dysfunction and possibly absent brachial or radial pulsation.
Cervical myelopathy usually affects C6, C7 roots and is unlikely to account for the gross wasting of the right hand. Joint position and vibration sense are often lost in the legs and there is often very little sensory loss of the hands.