An unusual differential diagnosis of suspected deep vein thrombosis

G. Hoyle1, Z. Smeed2.
1 Dr Graeme Hoyle, Specialist Registrar Medicine for the Elderly, Woodend Hospital, Eday Road, Aberdeen, AB15 6XS. Email: graeme.hoyle@nhs.net
2 Dr Zoë Smeed, FY1, Aberdeen. Email: zoesmeed@nhs.net

Abstract
Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) is an acquired neuropathy with a wide range of clinical presentations and a variable clinical course. We describe a case of CIDP presenting initially as unilateral thigh pain. This case highlights the difficulties in diagnosis of CIDP, and the differentiation between CIDP and Acute Inflammatory Demyelinating Polyneuropathy (Guillian-Barré Syndrome).

Case history
A previously independent 75 year old woman presented to her general practitioner with a 2 week history of right thigh pain. Past medical history included benign essential tremor, hypothyroidism and hypercholesterolaemia, treated with propanolol, thyroxine and simvastatin. The attending General Practitioner felt there was some swelling of the leg, and she was admitted to hospital for exclusion of deep vein thrombosis. Doppler ultrasound revealed a small popliteal cyst but no evidence of thrombus. She was subsequently discharged without diagnosis of her thigh pain.

Over the following 2 months, she had progressive worsening of pain in her right thigh, and additionally developed pain in her left thigh. The description of the pain was most consistent with myalgia and both thighs were tender to touch. Her GP discontinued the statin, but this failed to help her symptoms. Blood tests including ESR and CK were unremarkable.

Gradually her mobility deteriorated such that, despite increased help from her family and community physiotherapy involvement, she had frequent falls at home and became largely bedfast. Her declining mobility precipitated hospital admission. Her major complaint continued to be of bilateral myalgic thigh pain.

Neurological examination on admission revealed decreased power of both legs, more pronounced proximally, and right leg more so than left. There was subtle decreased power of both upper limbs. Knee and ankle jerks were absent bilaterally. Sensation was fully intact but both thighs were tender. There were no other significant findings on general examination. More detailed history revealed she had experience a short-lived diarrhoeal illness around two weeks before the initial onset of thigh pain.

MRI scan of lumbo-sacral spine demonstrated no evidence of cauda equina or nerve root compression. Lumbar puncture demonstrated raised CSF protein level (1128mg/L, normal range 0 – 700), normal CSF glucose and negative microscopy, consistent with our suspected diagnosis of inflammatory demyelinating polyradiculoneuropathy.

She was treated with intravenous immunoglobulins, and this, combined with intensive physiotherapy, led to a slow improvement (though not full resolution) of her leg power and mobility, eventually allowing discharge home after a number of weeks.

Discussion
Acute Inflammatory Demyelinating Polyradiculoneuropathy (AIDP, also known as Guillian-Barré Syndrome) is the commonest cause of acute, flaccid paralysis in developed countries1, characterised by rapid progressive limb weakness and areflexia1,2. In contrast Chronic Inflammatory Demyelinating Polyradiculoneuropathy (CIDP) follows a chronic progressive or relapsing-remitting course. Diagnosis is reached through corroborative history and the finding of raised CSF protein levels without increase in cellularity. Supportive evidence can be obtained with nerve conduction studies.

Symptoms of AIDP typically peak within 3-4 weeks whereas CIDP may progress gradually over months3. Approximately 60-70% of patients can recall a preceding event (typically gastrointestinal or respiratory infection) around 1-3 weeks prior to the development of symptoms of AIDP3. In comparison, less than one third of patients with CIDP can identify a preceding event3. The clinical situation in this case is consistent with a diagnosis of CIDP, given that there was apparent progression over 8 weeks, though the delay in presentation makes it difficult to be certain when the peak of symptoms occurred.

Although pain is a frequent associated symptom of AIDP (occurring in 72% of patients), it is rarely the chief presenting symptom4. Pain is much less common in CIDP, and it is highly unusual to be the major presenting symptom. In a case series presented by Boukhris et al5, 5 of 27 patients presenting with a diagnosis of CIDP over the course of two years described pain as the major presenting feature, but of these, three presented with radicular pain and two with bilateral distal lower limb pain rather than the myalgic pain prominent in this case. Myalgic pain is a frequently reported feature of AIDP, and other subtypes of pain such as paraethesia, dysaesthesia, axial and radicular pain, meningism, joint pain and visceral discomfort are also described4.

First-line therapy for CIDP consists of oral or parenteral corticosteroids or intravenous immunoglobulin therapy, in addition to physiotherapy. Both immunoglobulin therapy and corticosteroids have disadvantages, in particular the long-term adverse effects of corticosteroids and the expense of immunoglobulins6 and there is little consensus on the most appropriate initial therapy. There is growing recent evidence from randomised controlled trials that intravenous immunoglobulins offer significant benefit over placebo.

Conclusion
This case illustrates some of the difficulties in determining the difference between AIDP and CIDP at initial presentation. Pragmatically, treatment for both conditions is similar, with intravenous immunoglobulin an accepted first line therapy for both, leading to gradual improvement in this case. The insidious presentation with the most prominent symptom being myalgia and little other neurological deficit initially (or so is assumed by the patient being ambulant at time of suspected DVT) is unusual for CIDP, and it should be remembered that both AIDP and CIDP can present atypically. As Pentland4 points out, quoting the author Joseph Heller’s account of his own battle with Guillian-Barré Syndrome, “Typical of this rare and special form of polyneuritis is that so few cases are typical” 7.

References

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