In a total of 19 previous studies, from 1970 to 2014, different sizes of needles were compared (Table 4.2). Two study groups detected no differences in the compared needle sizes (20G vs. 22G, 23G vs. 25G) (Hammond et al. 2011; Kim and Yoon 2011); three other articles described a positive effect, such as faster collection time and less failures, when larger-bore needles were used (Ellis et al. 1992; Ready et al. 1989; Kokki and Hendolin 1996), whereas the majority of studies suggest the use of smaller-diameter needles (Hatfield et al. 2008; Lambert et al. 1997; Flaatten et al. 1998; Wilkinson and Sellar 1991; Aamodt and Vedeler 2001; Muller et al. 1994; Kleyweg et al. 1998; Vilming et al. 2001; Tourtellotte et al. 1972; Kaukinen et al. 1981; Crock et al. 2014; Lowery and Oliver 2008; Kovanen and Sulkava 1986; Palmers et al. 2002; McConaha et al. 1996; Tung 2013; Stendell et al. 2012). The articles reported a lower incidence of PLPH, low back pain, and discomfort and consequently a reduced use of medical assistance and medication after the procedure, when using small-diameter needles. Needles with a smaller diameter are also normally used to reduce the risk of PLPH and to avoid blood contaminations, defined as >5/μL red blood cells in the first tube of CSF collected (Armon et al. 2005).

In diagnostic context, LPs are often performed with larger-gauge needles (20–22G), whereas for therapeutic purposes, the needles are more narrow (25–27G) (Ginosar et al. 2012; Boon et al. 2004).

Reasons for using large-bore spinal needles include the increased speed in obtaining CSF samples by passive flow and the shorter time required to equilibrate the CSF pressure, when using a manometer. For CSF pressure measurement, needles smaller than 22G (thus >22G) are not suitable. Moreover, it is not recommended to use the smallest needle available because more technical difficulties occur, leading to failures, and because the duration of the procedure will be prolonged through the slow flow with these small spine needles (Flaatten et al. 1989). On the other hand, large needles are also not preferred as they produce large dural perforations with a higher risk of PLPH and contaminations. Needles used in children are selected based on the same criteria used for adults as described above.

In conclusion, a balance between the risk of PLPH, procedure duration, flow, and technical failure has to be considered for each patient individually (Turnbull and Shepherd 2003). The smallest needle as possible is recommended; however, longer sampling time and more failures should be taken into account for small-diameter needles, though with a reduced risk of PLPH, low back pain, and less discomfort. Nevertheless, in most centers, a 22G needle or larger needle diameter is used (Stendell et al. 2012; Birnbach et al. 2001). Once the practitioner is more confident, by often usage, the use of smaller needle types should be considered, which will lead to less failures and an easier procedure (Tung 2013).

Cutting bevel needles are still the standard needles mostly used in practice, because of the disadvantages of the atraumatic needles, such as low CSF flow and longer sampling time, little availability of these needles, less practical experience, a high failure rate, and the fact that when using local anesthetics, due to the thick introducer needle that penetrates the skin, it cannot be felt as well as with the standard needles when the dura is penetrated (Tung 2013; Stendell et al. 2012; Birnbach et al. 2001; Moller et al. 2013; Sharma et al. 1995). Needle types were compared in 35 studies between 1970 and 2014 (Table 4.3). No difference was reported in two studies (Quincke vs. Whitacre™) by comparing transdural fluid leakage and vascular trauma associated with blood contamination in CSF (Ready et al. 1989; Knowles et al. 1999). Three studies investigated the incidence of post-LP complications, such as PLPH and low back pain, and found no differences for all comparisons (Yale™ vs. Sprotte®, Spinocan® vs. Whitacre™, Quincke vs. an atraumatic needle type) (Aamodt and Vedeler 2001; Lenaerts et al. 1993; Luostarinen et al. 2005).

Nevertheless, in the 35 published articles, most studies recommended atraumatic needles as the best needle to perform LPs, when different needle types were compared (Table 4.3) (Alcolea et al. 2014; Hatfield et al. 2008; Lambert et al. 1997; Hammond et al. 2011; Muller et al. 1994; Kleyweg et al. 1998; Lowery and Oliver 2008; Palmers et al. 2002; Braune and Huffmann 1992; Ohman et al. 1995; Strupp et al. 2001; Tung et al. 2012; Vakharia and Lote 2012; Davis et al. 2014; Pedersen 1996; Kokki et al. 1999; Lavi et al. 2007; Lavi et al. 2006; Puolakka et al. 2000; Quinn et al. 2013; Carson and Serpell 1996; Thomas et al. 2000; Kokki et al. 2000; Reynolds and O’Sullivan 1998; Dakka et al. 2011; Vidoni et al. 2014). Advantages of the atraumatic needles are a lower incidence of PLPH, low back pain, and nausea/vomiting than cutting bevel needles, which consequently reduce healthcare costs as less medication and medical assistance, such as blood patches, are needed after the procedure (Cruickshank and Hopkinson 1989). Furthermore, lower incidence in traumatic taps is described when atraumatic needles are used; however, more attempts and failures are reported for these needle types. No exact data is available concerning other post-LP complaints than PLPH, number of traumatic taps, or failures. The technical drawbacks of atraumatic needles can be overcome with more training, also within practice, and likewise, several authors conclude that the disadvantages seem less decisive if the reduced risk of PLPH and, therewith, the time and cost savings for the healthcare system are taken into account (Strupp et al. 2001; Tung et al. 2012; Linker et al. 2002; Peskind et al. 2005; Arendt et al. 2009), which especially holds true for younger patients who have a higher risk of PLPH than the elderly.