A rare complication of AML is the infiltration of the CNS by leukaemia cells. The exact incidence is unknown, but it is associated with low rates of remission and poor prognosis.
A lumbar puncture is not a routine diagnostic procedure in patients with AML. However, if CNS symptoms are present, then a lumbar puncture to sample the cerebrospinal fluid (CSF) is necessary.
CNS symptoms warranting a lumbar puncture include:
- Continuous spasms and muscle contractions
- Akathisia (motor restlessness)
- Parkinsonism symptoms (rigidity, tremor, irregular, jerky movements)
- Impaired memory and cognition
- Primitive reflexes (grasp sign and ataxic gait)
If the analysis of the CSF indicates leukaemia cells have penetrated the CNS, patients will require additional treatment straight after diagnosis.
Lumbar puncture technique
Patients can either lie on their side with their legs pulled up, or sit up and lean forward. This makes it easier for the doctor or nurse to insert the needle between the L3-L4 vertebrae. (Figure 6).
Source: Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014”. Own work . WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436.
An imaginary line between the two posterior iliac crests corresponds to the level of L3-L4 for insertion of the needle. Palpation of the spinous processes helps locate the correct area between the vertebrae.
The healthcare professional performing the lumbar puncture, cleans and numbs the area, and then inserts a thin aspiration needle. A small amount of CSF is withdrawn.
Patients should not be in pain, but might feel some pressure.