Dry spinal tap due to primary psoas and paraspinal abscesses.

Sir,

Dry spinal tap, which is the condition when there is no cerebrospinal fluid (CSF) flow despite the correct placing of the spinal needle, is a worrying condition for physicians.[1] Although spinal taps for CSF studies are commonly performed in intensive care, dry tap has not been reported yet. In this study, we share one interesting case where primary psoas abscess led to dry tap.

A 74-year-old teacher presented to our hospital with mild backache and bilateral lower limb weakness for 2 weeks and high-grade fever (maximum 103° F) for 2 days. He had poorly controlled diabetes mellitus type 2 for 10 years Hemoglobin A1C (HbA1C=7.5). On examination, he was conscious but confused (glasgow coma scale 13-14), had 2/5 power in both lower limbs with equivocal planter reflexes with normal hemodynamics, and respiratory and oxygenation parameters. A non-healed ulcer in the left ankle was also noted. His sensorium deteriorated further in the next day though his renal, liver, and electrolyte profiles were normal. Brain magnetic resonance imaging (MRI) revealed age-related cerebral atrophy. An attempt for lumber puncture was tried by the neurophysician at the L3-L4 space with a 22G Quincke spinal needle. After multiple attempts in the central and paramedian plane, there was a free discharge of 2-3 ml straw-colored fluid. The total leukocyte count from that fluid was around 1 lakh; culture showed growth of methicillin-sensitive staphylococcus aureus, and it was negative for acid fast bacillus. Additionally, his subsequent blood cultures (repeated) were sterile and HIV 1 and 2 Enzyme linked immune sorbant assay were negative. Vancomycin was started in view of suspected pyogenic meningitis. Although his sensorium recovered, no improvement in weakness was noted even after a week. Internists retried lumber puncture at the L2-L3 space with a 22G Quincke spinal needle and again landed up with dry spinal tap despite appreciation of the ‘give-away feeling’ twice. Dorsolumbar spine MRI was carried out, which reported bilateral psoas abscess (R>L), with abscess in posterior spinal muscles with diffuse dural enhancement of the lumber cord (suggestive of arachnoiditis) and below-normal amount of CSF spaces in the lumber region [Figure 1] with normal lumber vertebrae and epidural spaces. A computed tomography (CT) guided aspiration of pus was performed and later sent for culture, which was found to be sterile. The patient's weakness reduced within 3 days. His ankle ulcer was also treated accordingly.

Figure 1

Magnetic resonance imaging T1 weighted view of multiple bilateral psoas (1) and paraspinal muscle abscesses with increased dural enhancement (2) with minimum cerebrospinal fluid in lumber subarachnoid space (triangle)

Primary psoas abscess is an uncommon condition of pus collection in the psoas muscle compartment due to hematogenous spread from a distant source.[12] The compartment is retroperitoneal and extends from the lateral border of the lower thoracic to the lower lumber vertebrae.[3] Our patient had long-standing uncontrolled diabetes mellitus and non-healed ulcer in the left ankle. The highly vascular psoas muscle might have got hematogenous infection from the ulcer.[12] Bilateral primary psoas abscess extended to paraspinal muscle spaces and later involved arachnoidmater, leading to intense inflammation (arachnoiditis).[45]

Not only a wrong technique and blocked needle, but also low CSF volume and pressure can lead to dry spinal tap.[6] Epidural abscess has been described as a cause of dry tap recently.[1] In our case, bilateral psoas abscess-mediated arachnoiditis caused adhesion of duramater and arachnoidmater and obliteration of the subarachnoid space in the thoraco-lumber area. Dry tap in our case was basically due to less CSF amount owing to this inflammatory adhesion; we believe ultrasound guidance[7] might help in successful spinal tap in this situation.