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A 25-year-old man presented with a 2-month history of pain in the lower neck and upper back with radiation along the inner aspect of the left upper limb, increasing on neck movements and straining. There was an associated history of progressive weakness and wasting of the left hand and an inability to perform skilled, fine movements with it. There was a complete loss of all sensations over the inner aspect of hand (ring and little finger) and inner aspect of the forearm. The rest of the left upper limb, the right upper limb and both the lower limbs were normal. There were no abnormal movements and no bowel or bladder disturbances. There was no history of fever, anorexia, weight loss, lassitude, bleeding tendencies, bone pains, or significant past or family history of similar complaints.
Examination revealed a young man, with a pulse rate of 82 beats/min, regular, and blood pressure 110/70 mmHg with pallor. There were no petechiae, lymphadenopathy, bone pains or rash. The chest, cardiovascular and abdominal examinations were normal. Nervous system examination revealed normal higher mental functions and no cranial nerve involvement. Both the lower limbs and the right upper limb were normal. Marked wasting of the small muscles of the left hand and medial half of forearm was evident. The muscle power in the individual muscles of the hand was 0/5. Wrist flexion (power 2/5) and hand grip were weak. Power over the other muscle groups of the left upper limb was normal. The biceps and supinator deep tendon reflexes were normal. Inversion of the triceps reflex was present, the plantar response was flexor and the Hoffman's sign was absent. Sensory loss to all modalities corresponding to the C8 and T1 spinal cord segments was seen. There were no abnormal movements or cerebellar signs. The optic fundi were normal. Examination of the spine revealed tenderness along the bodies of the sixth, and seventh cervical and first thoracic vertebrae.
The X-rays of the spine were normal. Magnetic resonance imaging (MRI) of the spine was done and is depicted in figure 1. The results of routine laboratory investigations revealed a haemoglobin of 8.0 g/dl, total leucocyte count 24.9 × 109/l and platelet count 65 × 109/l; peripheral blood smear revealed normocytic, hypochromic red blood cells and a differential leucocytic count of 50% polymorphs, 10% lymphocytes, 2% monocytes, 1% eosinophils, 22% myeloblasts, 10% promyelocytes, 6% myelocytes, and 4% metamyelocytes. A special investigation was done and is depicted in figure2.
- What is the clinical diagnosis?
- Discuss the MRI findings.
- What was the special investigation and what is the underlying disorder?
- What is the final diagnosis?
The patient presented with a history of typical radicular pain along the left C7-8 and C8-T1 nerve roots associated with muscular wasting, inversion of the left triceps reflex and sensory loss corresponding to these spinal segments suggesting the diagnosis of a radiculopathy of C7-8, C8-T1 nerve roots, possibly due to a compressive lesion.
The MRI scan reveals a soft tissue extradural mass of isointense signal extending from the upper border of the sixth to the middle of the body of the second thoracic vertebrae and extending into the neural canals at C5-6, C6-7, C7-T1 levels. The anterolateral aspect of the thecal sac is compressed at these levels. The spinal cord is normal.
A bone marrow aspiration was performed, which revealed a hypercellular marrow with infiltration of the marrow with numerous myeloblasts with evidence of maturation, FAB subtype M2, suggestive of acute myeloid leukaemia (AML) FAB-M2.
The final diagnosis is AML (M2) with an extradural leukaemic deposit from C7-T1 leading to a radicular syndrome.
Central nervous system (CNS) involvement in acute leukaemias is not uncommon. It is usually seen as a manifestation of a relapse of the leukaemia. Prior to the routine use of prophylactic therapy against CNS leukaemia, the incidence of a meningeal relapse in adults and children with acute lymphocytic leukaemia (ALL) was almost 50%.1 With the advent of prophylactic therapy, this incidence has come down to 10%.2 The incidence of CNS relapse in adult AML is about 15%.3 CNS involvement at initial diagnosis in all acute leukaemias is very uncommon. In a large series of 222 adult patients with acute leukaemia (all subtypes), only two had CNS involvement at presentation,4an incidence of approximately 1%.
The CNS involvement in acute leukaemias reflects the unusual behaviour of the leukaemia cells or the unusual host reaction to the leukaemia cells.5 Nervous system involvement in acute leukaemias may take a number of forms (box FB1), of which leukaemic meningitis is the most common. Neurological involvement in AML has a few distinctive features (boxFB2).3 4
The importance of leukaemic deposits in the nervous system lies in the fact that these deposits are shielded from chemotherapeutic agents by the naturally existing blood–brain and blood–nerve barriers.6 The intrathecal route of instillation of chemotherapy by-passes the blood–brain barrier, but the blood–nerve barrier remains intact and these cells then serve as potential sources for a future relapse of the leukaemia.7
The treatment of CNS leukaemia includes cranial irradiation and intrathecal chemotherapy.5 Intrathecal chemotherapy is administered weekly until the cerebrospinal fluid is cleared of leukaemia cells and followed up with a maintenance intrathecal regimen, consisting of either methotrexate, cytarabine, or a combination of methotrexate, cytarabine and hydrocortisone. The optimal duration of intrathecal therapy is unclear. Patients with isolated CNS relapse should be treated with a systemic intensification regimen in addition to radiotherapy and intrathecal chemotherapy. Nervous system involvement in leukaemia worsens the overall prognosis of the disease.
The case we have reported is unusual in many respects. Nervous system involvement in AML per se is very uncommon and neurological manifestations at initial presentation of AML are extremely rare. Further more, we could find only three previous documentations of radicular syndromes in AML in the English literature3; all three cases represented a relapse of AML.
AML (M2) with an extradural leukaemic deposit from C7-T1 leading to a radicular syndrome.
The authors acknowledge the help of Dr D K Shome, Department of Pathology, Maulana Azad Medical College, New Delhi.
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