Page 2278 - Cote clinical veterinary advisor dogs and cats 4th

1132 Magnetic Resonance Imaging Scan

that side and adjacent soft tissues (includ- mandibular molar on the medial aspect Pearls
ing some nasal mucosa) of the mandible, and advance it along • Technicians should master nerve block
VetBooks.ir • Infraorbital nerve block ○ Extraoral: insert needle through skin at • Use a fresh sterile needle for each individual
bone surface in a caudoventral direction
○ Do not inject into the eye!
techniques for dental and oral surgical
procedures.
toward the mandibular foramen.
○ Intraoral: insert needle through labial
mucosa at the transverse level of the maxil-
○ Repeat use of same needle for more
mandible between its body and angular
lary second/third premolar in a caudal an unnamed notch of the caudoventral injection.
direction toward the infraorbital foramen process, and advance it on the medial than one injection increases risk of
(keep needle parallel to the hard palate aspect along the bone surface toward the infection.
when advancing it into the infraorbital mandibular foramen. ○ Repeat bumping onto bone causes needle
canal). ○ Areas desensitized: mandibular body, tip to bend, which may injure vessel/nerve
○ Extraoral: insert needle through lateral skin all mandibular teeth and adjacent soft upon needle retraction.
(similar to when going through mucosa tissues • Always aspirate before injection.
but not recommended because larger • Middle mental nerve block ○ If no vacuum is felt when going through
needle is needed). ○ Insert needle through labial mucosa skin upon placing maxillary or inferior
○ Areas desensitized: incisive bone and rostral to a frenulum-like fold between alveolar nerve blocks, needle tip may be
maxilla, maxillary incisors, canine, and the mandibular canine and first premolar located within oral cavity or oropharynx.
premolars/molars and adjacent soft tissues (dog) or third premolar (cat), and advance ○ Aspirate for several seconds with thinner
(depending how far needle is advanced it along the lateral bone surface in a needles, as it may take longer for blood
caudally into infraorbital canal; because caudoventral direction toward the middle to appear within syringe if needle tip is
infraorbital canal is short in cats, all mental foramen. indeed in vessel lumen.
maxillary tissues on that side can easily ○ Extraoral: insert needle through lateral skin • Keep needle steady during injection.
be desensitized) (similar to when going through mucosa ○ Ensure that needle is firmly attached to
○ Do not inject into the eye! but not recommended because larger the syringe before injection.
• Major palatine nerve block needle is needed). ○ Upon advancing the needle, one may enter
○ Insert needle through palatal mucosa ○ Areas desensitized: rostral mandibular a vessel and exit it again. For example,
at the transverse level of the main cusp body, teeth rostral to injection site retracting needle during injection may
of the maxillary third premolar between (mandibular incisors +/− canine) and position the needle tip back into a vessel
the median plane and dental arch, and adjacent soft tissues lumen.
advance it caudally just rostral to the major ○ In larger patients, you may enter the
palatine foramen (located palatal to the mandibular canal through the middle SUGGESTED READING
maxillary fourth premolar about halfway mental foramen. Beckman B: Anesthesia and pain management for
toward the median plane). small animals. Vet Clin North Am Small Anim
○ Areas desensitized: palatine shelf of the Postprocedure Pract 43:669-688, 2013.
maxilla and adjacent soft tissues • Apply digital pressure/perform brief massage AUTHOR: Alexander M. Reiter, DVM, Dr. med. vet.,
○ Some resistance felt during injection is of the injection site. DAVDC, DEVDC
expected because palatal mucosa does • Safely discard needle and syringe. EDITORS: Leah A. Cohn, DVM, PhD, DACVIM; Mark S.
not contain submucosa (slight bleb often • Monitor the injection site for hematoma Thompson, DVM, DABVP
visible after injection). formation.
• Inferior alveolar nerve block
○ Intraoral: insert needle through oral
mucosa immediately caudal to the last

Magnetic Resonance Imaging Scan

Difficulty level: ♦♦♦ uses include assessment of the brain and to oscillate in the patient. In human medi-
spinal column. Musculoskeletal imaging cine, MRI suites bear warnings forbidding
Synonyms (e.g., scapulohumeral joint, stifle) is also entry to any person with a pacemaker, and
MRI, MR increasingly commonplace in small animal it is unlikely that an MRI technician would
practice. allow a veterinary patient with a pacemaker
Overview and Goal to be scanned.
• Magnetic resonance imaging (MRI) is a Indications • Presence of ferrous (iron-containing) metal,
method of cross-sectional imaging that does • Disease of the central nervous system; best including implants and intestinal foreign
not involve ionizing radiation. Compared to method available for imaging of the brain bodies
radiography, MRI allows improved evaluation • Selected orthopedic, abdominal, and other ○ Movement of the metal when in the
of areas of complex anatomy by avoiding soft-tissue disorders magnetic field, causing soft-tissue trauma
superimposition of multiple structures. • Presence of large metallic implants (nonfer-
The contrast resolution of MRI is vastly Contraindications rous) in the area of interest:
superior to that of radiography and computed • Inability to tolerate general anesthesia ○ Heating of the metallic implants → tissue
tomography (CT). • Presence of a pacemaker: in a minority of damage.
• MRI can be used for assessing any area of patients, the MRI magnetic field alters the ○ Imaging artifact severely limits the value
the body. In veterinary medicine, common pacemaker program or causes the pacemaker of the study.

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