YPC   |   Support Groups   |   Choose Your Language:
     
  • Effect of Microvascular Decompression in Trigeminal Neuralgia Patients with or without Constant Pain

    Tiril Sandell, M.D.
    Department of Neurosurgery,
    Division of Clinical Neuroscience,
    The National Hospital (Rikshospitalet),
    Oslo, Norway
    Per Kristian Eide, M.D., Ph.D.
    Department of Neurosurgery,
    Division of Clinical Neuroscience,
    The National Hospital (Rikshospitalet),
    Oslo, Norway
    Reprint requests:
    Per Kristian Eide, M.D., Ph.D.,
    Department of Neurosurgery,
    Division of Clinical Neuroscience,
    The National Hospital (Rikshospitalet),
    N-0027 Oslo, Norway.
    Email: per.kristian.eide@rikshospitalet.no
    Received, August 15, 2007.
    Accepted, March 28, 2008.

    OBJECTIVE: To study the effect of microvascular decompression (MVD) in trigeminal
    neuralgia (TN) patients with or without constant pain.
    METHODS: The study includes all first-time MVDs for facial pain performed by the
    senior author (PKE) during the 6-year period from 1999 to 2005 in the Department of
    Neurosurgery at the National Hospital. At the time of follow-up, pain relief was assessed
    using a standard mail questionnaire; those patients still having residual pain were further
    examined in the outpatient clinic or interviewed by phone.
    RESULTS: The total study population includes 135 patients who underwent initial MVDs
    (67% of MVDs for TN without constant pain and 33% of MVDs for TN with constant
    pain). At the time of follow-up, the response rate was 95%, which provided us with
    128 patients. The median observation period was 38 months (range, 12–87 mo). For
    episodic pain, MVD caused complete (i.e., 100%) pain relief in 78% of TN patients
    without constant pain and in 77% of TN patients with constant pain before MVD, and
    a significant pain relief (i.e., worst pain marked as 0–3 cm on a 10-cm visual analog scale)
    in 85 and 81%, respectively. For constant pain, MVD caused complete pain relief in
    70% of the TN patients with constant pain before MVD, and significant pain relief in 77%.
    CONCLUSION: In TN patients with constant pain before MVD, significant relief of
    episodic and constant pain was observed in 81 and 77%, respectively. Hence, the presence
    of constant pain should not prevent TN patients from being offered MVD.
    KEY WORDS: Atypical trigeminal neuralgia, Constant pain, Microvascular decompression, Pain relief,
    Trigeminal neuropathic pain, Typical trigeminal neuralgia
    Neurosurgery 63:93–100, 2008 DOI: 10.1227/01.NEU.0000316856.32104.65 www.neurosurgery-online.com

    Trigeminal neuralgia (TN) usually has a rather typical
    clinical picture, with short-lasting episodic pain and
    trigger points (4, 5, 8, 11), but it is recognized that TN
    may include a constant pain that is burning, aching, and
    throbbing in character (4, 5, 8, 12). TN with constant pain
    (usually denoted atypical TN) represents a great diagnostic
    challenge for the neurosurgeon because of uncertainty as to
    whether the facial pain can be classified as TN or whether the
    facial pain is trigeminal deafferentation pain caused by previous
    neurodestructive procedures (4–7). Burchiel (4) has
    made recent efforts in standardizing the terminology of facial
    pains, differentiating between Type 1 TN (i.e., 50% episodic
    pain) and Type 2 TN (i.e., 50% constant pain) in addition to
    differentiating atypical TN from trigeminal neuropathic pain
    (Table 1).
    Although microvascular decompression (MVD) has a wellestablished
    role in the treatment of typical TN without constant
    pain, its role in treating TN with constant pain (atypical
    TN) remains less clear. The presence of a constant pain component
    has traditionally been considered a negative prognostic
    factor for MVD (9, 14); however, one recent report indicates a
    beneficial role of MVD even for atypical TN with constant pain
    (12). Nevertheless, more data are needed to determine the role
    of MVD in treating TN with constant pain.
    For this purpose, we examined our material from firsttime
    MVD procedures for facial pain during a 6-year period.
    During this period, the senior author (PKE) put special focus
    on differentiating between TN with and without constant
    pain during the preoperative assessment. Different from TN
    with 100% episodic pain, TN with constant pain was characterized
    by burning, aching, and throbbing pain in addition
    to the episodic pain, which is comparable to the clinical picture
    of trigeminal neuropathic pain (6, 7). MVD for TN with
    constant pain was performed exclusively in patients in
    whom the constant pain had developed from being exclusively
    episodic.

    PATIENTS AND METHODS

    Patients
    The study includes all patients (n  135) undergoing first-time MVD
    for facial pain (90 without and 45 with constant pain) in this hospital by
    the senior author (PKE) during the 6-year period from 1999 to 2005.
    Among the 135 patients, 24 (17.8%) had received previous neurodestructive
    procedures, namely percutaneous retrogasserian glycerol rhi-
    rhizotomy
    (PRGR) in 21 and peripheral alcohol in three. Patients with
    multiple sclerosis were excluded from the study. Preoperative demographic
    data were retrieved from patient records (Table 2).

    TN with or without Constant Pain

    The patients were categorized into the following categories depending
    on the presence or absence of a constant pain component before
    MVD and at follow-up:
    1) Type 1a: TN with 100% episodic pain characterized by exclusively
    episodic pain lasting seconds to a few minutes, typically shooting
    and electrical in character. The pain can be evoked, typically with
    trigger points present. There are pain-free intervals.
    2) Type 1b: TN with greater than 50% episodic pain characterized by
    episodic pain lasting seconds to a few minutes, typically shooting and
    electrical in character. In addition, constant pain is present day and
    night with a burning, aching, and throbbing character. The episodic
    pain component predominates over the constant pain component.
    This facial pain is comparable to Type 1 according to Burchiel (4).
    3) Type 2: TN with greater than 50% constant pain characterized by a
    constant pain present day and night with a burning, aching, and
    throbbing character. Although this pain is constant, its intensity is
    fluctuating. The pain is spontaneous and typically nonevoked,
    though episodic pain may be present. This facial pain is comparable
    to Type 2 according to Burchiel (4). Although the clinical picture is
    comparable to that of trigeminal neuropathic pain (6, 7), TN with
    constant pain (typically denoted atypical TN) is not synonymous
    with trigeminal neuropathic pain, nor are its causes, which include
    previous surgery, trauma, or stroke. Hence, trigeminal neuropathic
    pain should be differentiated from TN with constant pain (Type 2, or
    atypical TN) (Table 1). It should be emphasized that our TN patients
    with constant pain (Types 1b and 2) initially had TN without constant
    pain (Type 1a). TN with constant pain (Types 1b and 2) may
    also occur de novo.

    Radiological Assessment of Neurovascular Compression

    The presence of neurovascular conflict between the affected trigeminal
    nerve and an offending vessel was assessed by preoperative magnetic
    resonance angiography (MRA), using a three-dimensional timeof-
    flight MRA sequence and a T2-weighted three-dimensional
    sequence. The MRA findings were compared with the perioperative
    observations during the MVD procedure (Table 3).

    MVD

    Indication for MVD was clinical and based on the patient history, i.e.,
    the presence of TN with or without constant pain when constant pain
    had evolved from exclusively episodic pain. This was noted in the
    patient records. All patients underwent MVD in the park bench position.
    With the use of a small retrosigmoid craniectomy, an opening in the
    dura (1.5–2 cm) was made in the angle between the sigmoid and transverse
    sinuses. Microsurgery on the trigeminal nerve was made via a lateral
    cerebellar approach without using a retractor. Arteries were
    removed from the nerve and kept away from the nerve with a piece of
    Teflon (DuPont, Wilmington, DE) while compressing veins were coagulated
    and divided. The least possible manipulation of the trigeminal
    nerve was attempted. Watertight closure of the dura was performed
    under a microscope. Perioperative and neurological complications of
    surgery were recorded (Table 4).

    Clinical Assessment of Pain Relief

    Follow-up assessment was performed by the first author (TS), who
    was not involved in the management or surgery of the patients during
    the study period. All patients received a questionnaire by mail;
    the patients were asked to state whether facial pain had disappeared
    completely (100%) without any signs of residual pain (and no medication
    needed) or whether some facial pain was still present. Those
    patients still having facial pain were seen at our outpatient clinic and
    examined by the first author (TS). Those who were not able to meet
    (e.g., because of age, travel distance, or other diseases) were interviewed
    by phone. Clinical differentiation between residual TN with
    or without constant pain was made. To assess the degree of residual
    pain, a visual analog scale (VAS) of 0 to 10 cm was used to indicate
    the patient’s worst intensity of residual pain (episodic and constant
    pain components) (Tables 5 and 6). Pain relief was defined as complete
    when facial pain had disappeared completely (100%) and as significant
    when worst pain on the VAS was 0 to 3 cm. Complete pain relief
    implied that no medication was taken.

    Statistical Analysis

    Statistical analysis was performed using PC-SPSS software version
    12.0 (SPSS, Inc., Chicago, IL). Comparisons among groups (Types 1a,
    1b, and 2) were performed using an independent-samples Student’s t
    test for continuous data and χ2 test for categorized data. Significance
    was accepted at the 0.05 level.

    RESULTS

    Patients and Pain Types

    The patient data included a total of 135 first-time MVD procedures.
    Demographic preoperative data are shown in Table 2.
    There were no significant differences between TN patients
    with or without constant pain regarding age, duration of pain
    before MVD, or duration of follow-up after MVD (P  0.1;
    independent-samples Student’s t test). Microvascular decompression
    was performed for TN with 100% episodic pain (Type
    1a) in 67% and for TN with constant pain (Types 1b and 2) in 33%.
    Neurodestructive treatment had been performed previously
    in 24 patients undergoing MVD procedures (PRGR in 21 and
    peripheral alcohol in three), in 14 of 90 (16%) TN patients with
    100% episodic pain (Type 1a), and in eight of 31 (26%) TN
    patients with more than 50% constant pain (Type 2); hence, a
    slight (nonsignificant) overrepresentation of previous neurodestructive
    treatment in those TN patients with constant pain is
    represented (Table 2).

    Assessment of Neurovascular Conflict

    MRA showed neurovascular contact in 97 of 135 trigeminal
    nerves (72%) and no neurovascular contact in 28 (21%); preoperative
    MRA was not available for 10 (7%) (Table 3).
    Perioperative neurovascular compression was found in 129
    MVD procedures (96%) (Table 3), which included a neurovascular
    contact in 24 of the 28 MRA-negative observations (86%). A
    single venous compression was observed in 25.8% of the TN
    Type 2 group versus 15.6% in the TN Type 1a group, which did
    not reach significance (P  0.08, Pearson χ2 test) (Table 3).

    Complications of MVD

    The perioperative and neurological complications of MVD
    are presented in Table 4. Only one complication was encountered
    in each patient. Acute perioperative complications (not
    causing lasting complaints in any of the patients) were
    observed in eight of 135 (6%) procedures. The worst complication
    was in an 84-year-old woman who developed swelling in
    her right cerebellar hemisphere that required a partial cerebellar
    hemispherectomy after a few hours. Despite her age, she
    recovered well, remaining pain-free. A 72-year-old man who
    underwent an uneventful MVD was mobilized the first postoperative
    day and recovered pain-free without any deficits, soon
    returning to his home. Four weeks after surgery, without preceding
    symptoms, he was found dead in his home; the cause of
    death remains unknown.
    At the time of follow-up, lasting problems were reported
    after 18 (14%) of 128 MVDs. Five (4%) of 128 had persistent
    facial numbness postoperatively; one of the five (with typical
    TN) had had facial numbness before MVD. Six (4.7%) patients
    had problems with dizziness. No patient had postoperative
    hearing loss, although different degrees of subjective postoperative
    hearing dysfunction were reported in seven of 128 (6%)
    procedures.

    Assessment of Residual Facial Pain

    For assessment of residual facial pain after surgery, seven
    patients were lost to follow-up (i.e., 95% response rate), leaving
    a total of 128 initial MVD procedures. The median follow-up
    period was 38 months (range, 12–87 mo).
    Pain relief after MVD in relation to preoperative type of facial
    pain is shown in Table 5. Among 85 MVD procedures in the TN
    patients with 100% episodic pain (Type 1a), 66 (78%) patients
    had complete (100%) relief from episodic pain, whereas an
    additional six (7%) patients had significant pain relief (VAS,
    1–3 cm) (see Table 5). We found no significant differences in
    relief from episodic pain among patients who had 100%
    episodic pain before MVD (Type 1a), had more than 50%
    episodic pain (Type 1b), and had more than 50% constant pain
    (P  0.79) (Table 5).
    In those TN patients with constant pain, 77% of the MVD
    procedures caused complete relief of episodic pain. This finding
    was observed in both the TN patients with more than 50%
    episodic pain (Type 1b) and those with more than 50% constant
    pain (Type 2) (Table 5). Significant relief from episodic pain was
    observed in 81% in the Type 2 group. Complete freedom from
    constant pain was observed after 11 (85%) of 13 MVDs in those
    with more than 50% episodic pain (Type 1b) and after 19 (63%)
    of 30 MVDs in those with more than 50% constant pain (Type
    2) (P  0.001, Pearson χ2 test) (Table 5). Hence, freedom from
    constant pain was less likely in those who had developed predominant
    constant pain (Type 2) than in those with predominant
    episodic pain in addition to constant pain (Type 1b).
    We also separately analyzed the 24 patients who had previously
    received neurotoxic treatment (PRGR in 21 and peripheral
    alcohol in three patients). As shown in Table 6, pain relief
    after MVD was not worse in this subgroup, as compared with
    the total group (Table 5).

    DISCUSSION

    The main observation is that at a median 38 months after
    MVD, significant relief of both episodic and constant pain was
    found in a high proportion of TN patients with constant pain
    before MVD (Types 1b and 2).

    Classification of Facial Pain

    Unfortunately, there are no universally accepted classifications
    of facial pain. The term typical TN usually refers to TN
    with only episodic pain and trigger points (11), whereas TN
    with constant pain (usually denoted atypical) represents a
    diagnostic challenge (4, 5, 8). According to our tradition, we
    consider TN as atypical when it includes a component of constant
    pain that is aching, burning, and throbbing in character;
    the classification refers to the clinical picture rather than the
    cause of facial pain (6, 7). TN can be considered a unique form
    of neuropathic pain (5). The International Association for the
    Study of Pain defines neuropathic pain as pain initiated or
    caused by a primary lesion or dysfunction in the nervous system
    (11). Hence, in our TN patients with constant pain (Types
    1b and 2), the neurovascular compression can be considered
    the primary lesion. This lesion is different from anatomic
    lesions caused by, for example, stroke, tumor, surgery, or
    trauma; in such cases, the term secondary TN is used (11).
    Symptomatic TN refers to that caused by multiple sclerosis. It
    should be emphasized that a neurodestructive procedure cannot
    produce atypical TN (Types 1b and 2), but deafferentation
    pain, which should not be treated as TN.
    The Burchiel classification scheme for facial pains does not
    use the terms typical and atypical TN (4, 8). As shown in Table
    1, it distinguishes between Type 1 TN, with more than 50%
    episodic pain and Type 2 TN, with more than 50% constant
    pain. Trigeminal neuropathic pain is used exclusively for neuropathic
    facial pain caused by trauma (4, 8). Other authorities
    in the field, such as Sindou et al. (12), use the term atypical TN
    for TN with constant pain. Because taxonomy still remains a
    topic of discussion, we differentiate between TN with 100%
    episodic pain (Type 1a), TN with more than 50% episodic pain
    (Type 1b, comparable to Burchiel Type 1 TN), and TN with
    more than 50% constant pain (Type 2, comparable to Burchiel
    Type 2 TN).

    Patients

    In our study, MVD was performed for TN without constant
    pain (Type 1a) in 67% and for TN with constant pain (Types 1b
    and 2) in 33% of patients. These numbers are comparable with
    the study by Sindou et al. (12) of 362 patients, consisting of
    65.5% with typical TN and 35.5% with atypical TN (i.e., presence
    of constant pain).
    There are several reasons why a rather high proportion of TN
    patients developed constant pain (Types 1b and 2) at the time
    of MVD. For all MVD procedures, the median duration of pain
    was 5 years. Development of constant pain may be a part of the
    natural course of TN (5). Another possibility is that constant
    pain developed in the course of previous destructive procedures
    (6, 7); there was a slight, nonsignificant overrepresentation
    of previous neurodestructive procedures in the Type 2 TN
    group. In such cases, the atypical TN should be classified as
    trigeminal deafferentation pain (see Table 1), because a neurodestructive
    procedure cannot produce TN. The clinical examination
    of our patients did not indicate deafferentation pain.
    The observation that patients previously treated with a neurodestructive
    procedure did not experience less pain relief than
    the whole group may support this conclusion.
    This report does not give a clear answer as to why 33% of the
    TN patients had developed constant pain (Types 1b and 2). In
    comparison with TN patients without constant pain (Type 1a),
    TN patients with constant pain (Types 1b and 2) were not significantly
    older, and their pain had not lasted significantly
    longer (Table 2). Regarding their type of vascular compression,
    there were no significant differences (Table 3). There only was a
    slight, nonsignificant overrepresentation of previous neurodestructive
    procedures (PRGR or peripheral alcohol) in those with
    constant pain (Type 2) (Table 2). At the time of follow-up,
    hypoesthesia was found in 2.4% of those without constant pain
    (Type 1a), but in approximately 7% of those with constant pain
    (Types 1b and 2) (Table 4). Another aspect not explored here is
    possible differences in psychological profile.
    Indications for MVD were based on pain history. In the preoperative
    assessment, the senior author (PKE) strove to delineate
    whether or not constant pain (Types 1b and 2) had developed
    from exclusively episodic pain (Type 1a). It should be
    stressed that MVD was performed only in TN patients in
    whom constant pain had developed from first being exclusively
    episodic. Hence, in the present 135 patients, facial pain,
    after first being 100% episodic, had changed to include a constant
    pain characterized by burning, aching, and throbbing,
    present day and night. However, patients with a clinical picture
    of trigeminal neuropathic pain without a history of facial pain
    indicative of TN, but with a history of previous stroke, trauma,
    or surgery, were not considered for MVD. Hence, no patients
    with pain caused by a previous injury or deafferentation were
    offered MVD. In this respect, it can be discussed whether the
    facial pain in the 10 TN patients with constant pain who had
    been treated previously with PRGR or alcohol qualified as
    trigeminal deafferentation pain. Because our clinical examination
    did not indicate that PRGR had caused deafferentation, we
    decided to include these 10 patients. Nevertheless, in TN
    patients who have previously received a neurodestructive procedure,
    it can be a diagnostic challenge to determine whether
    or not the constant pain represents deafferentation pain.

    Neurovascular Contact

    In our experience, the use of MRA revealed a neurovascular
    contact in approximately 70% of the nerves. The success rate
    may have been increased by the use of other magnetic resonance
    imaging modalities. Nevertheless, these results underline
    that the MVD indication should primarily be based on clinical
    reasoning; in our practice, MRA is only used as an aid secondary
    to the pain history.

    Complications of Surgery

    The present data show a rather favorable profile regarding
    complications from MVD, which is in line with the reports of
    previous series (10). In earlier reports, a greater complication
    rate of MVD was reported (15). As expected, the complication
    profile was similar among the different pain categories. A disadvantage
    is that it was unclear whether hearing dysfunction
    was present before surgery as well.

    Pain Relief after Surgery Depending on Type of Pain

    At a median of 38 months after MVD, we found that in TN
    patients with 100% episodic pain (Type 1a) complete (i.e.,
    100%) relief of pain was achieved in 78% and significant pain
    relief (i.e., worst pain being 0–3 cm on a 10-cm VAS) was
    achieved in 85%. These numbers are comparable with previous
    reports (1–3, 13, 15), thus contributing to the extensive literature
    that MVD causes lasting relief from episodic pain in a high
    proportion of patients.
    Among those 15% in whom MVD failed to relieve pain, constant
    pain was present in 4.7%. This number could result from
    the natural course of TN. It appears less likely that the observation
    relates to the MVD procedure itself because least possible
    manipulation of the trigeminal nerve was attempted.
    Although the literature on MVD for TN with episodic pain is
    extensive, less attention has been given to effects of MVD in TN
    patients with constant pain (9, 14). The general view among
    neurosurgeons has been that MVD is less effective for TN with
    constant pain.
    The most important observation of this study is that MVD
    for TN patients with constant pain (Types 1b and 2) resulted in
    complete relief of episodic pain in 77% and significant pain
    relief in 81%. Complete (100%) relief of constant pain was
    observed in 85% of the group with more than 50% episodic
    pain (Type 1b) and 63% of the group with more than 50% constant
    pain (Type 2) before MVD; significant relief of constant
    pain (i.e., worst constant pain being 0–3 cm on a 10-cm VAS)
    was observed in 71% of the Type 2 group. With a median observation
    period of 38 months, these numbers are high. The percentages
    are comparable to the results of Sindou et al. (12),
    who reported relief of atypical TN after MVD. However, the
    results do not support earlier data that the presence of constant
    pain represents a negative prognostic factor for MVD (14).
    The most important reason for differences among data probably
    relates to the selection of patients. The present data apply
    only to TN patients who have developed constant pain (Types
    1b and 2) after initially having episodic pain (Type 1a). We
    would expect the results of MVD to diminish dramatically if
    patients with trigeminal neuropathic pain, e.g., caused by stroke,
    trauma, or surgery, or deafferentation after a neurodestructive
    procedure, were included among those receiving MVD.
    Thus, the major lesson from this data is that in one-third of
    TN patients, episodic facial pain had developed into a constant
    facial pain of burning, aching, and throbbing character that
    was continuously present, day and night, in addition to their
    episodic pain (Types 1b and 2). After MVD, both the episodic
    and the constant pain components disappeared in a high proportion
    of patients. It should be noted, however, that the chance
    of being free from constant pain was significantly lower when
    constant pain had become predominant (Type 2) as compared
    with a situation in which episodic pain still was predominant
    (Type 1b) (Table 5).

    CONCLUSION

    Among TN patients who have developed constant pain in
    the course of their disease, MVD produces relief of both
    episodic and constant pain components in a significant proportion.
    The data support a role for MVD for TN even after
    episodic pain has developed into constant pain. It is important
    to stress that, in our TN patients with constant pain (Types 1b
    and 2), the TN had evolved from exclusively episodic (Type 1a).
    Hence, a careful delineation of the pain history is crucial in the
    preoperative assessment.

    REFERENCES

    1. Barker FG 2nd, Jannetta PJ, Bissonette DJ, Jho HD: Trigeminal numbness and
    tic relief after microvascular decompression for typical trigeminal neuralgia.
    Neurosurgery 40:39–45, 1997.
    2. Barker FG 2nd, Jannetta PJ, Bissonette DJ, Larkins MV, Jho HD: The long-term
    outcome of microvascular decompression for trigeminal neuralgia. N Engl J
    Med 334:1077–1083, 1996.
    3. Broggi G, Ferroli P, Franzini A, Servello D, Dones I: Microvascular decompression
    for trigeminal neuralgia: Comments on a series of 250 cases, including
    10 patients with multiple sclerosis. J Neurol Neurosurg Psychiatry
    68:59–64, 2000.
    4. Burchiel KJ: A new classification for facial pain. Neurosurgery 53:1164–1167,
    2003.
    5. Burchiel KJ, Slavin KV: On the natural history of trigeminal neuralgia.
    Neurosurgery 46:152–155, 2000.
    6. Eide PK, Rabben T: Trigeminal neuropathic pain: Pathophysiological mechanisms
    examined by quantitative assessment of abnormal pain and sensory
    perception. Neurosurgery 43:1103–1110, 1998.
    7. Eide PK, Stubhaug A: Relief of trigeminal neuralgia after percutaneous retrogasserian
    glycerol rhizolysis is dependent on normalization of abnormal temporal
    summation of pain, without general impairment of sensory perception.
    Neurosurgery 43:462–474, 1998.
    8. Eller JL, Raslan AM, Burchiel KJ: Trigeminal neuralgia: Definition and classification.
    Neurosurg Focus 18:E3, 2005.
    9. Frazier CH, Russell EC: Neuralgia of the face, an analysis of 754 cases with
    relation to pain and other sensory phenomena before and after operation.
    Arch Neurol Psychol 11:557–563, 2003.
    10. Kalkanis SN, Eskandar EN, Carter BS, Barker FG 2nd: Microvascular decompression
    surgery in the United States, 1996 to 2000: Mortality rates, morbidity
    rates, and the effects of hospital and surgeon volumes. Neurosurgery
    52:1251–1262, 2003.
    11. Merskey H, Bogduk N: Classification of Chronic Pain. Seattle, IASP Press, 1994.
    12. Sindou M, Leston J, Howeidy T, Decullier E, Chapuis F: Micro-vascular
    decompression for primary trigeminal neuralgia (typical or atypical). Long
    term effectiveness on pain; prospective study with survival analysis in a consecutive
    series of 362 patients. Acta Neurochir (Wien) 148:1235–1245, 2006.
    13. Slettebø H, Eide PK: Aprospective study of microvascular decompression for
    trigeminal neuralgia. Acta Neurochir (Wien) 139:421–425, 1997.
    14. Szapiro J Jr, Sindou M, Szapiro J: Prognostic factors in microvascular decompression
    for trigeminal neuralgia. Neurosurgery 17:920–929, 1985.
    15. Taha JM, Tew JM Jr: Comparison of surgical treatments for trigeminal neuralgia:
    Reevaluation of radiofrequency rhizotomy. Neurosurgery 38:865–871, 1996.

    COMMENTS

    Microvascular decompression (MVD) is a highly effective, well-documented
    treatment for the lancinating pain of trigeminal neuralgia
    (TN). However, there is less agreement regarding the effectiveness of
    MVD for “atypical” TN, in which constant rather than episodic pain
    predominates. In this study, Sandell and Eide evaluated results in two
    groups of patients: those with typical, lancinating pain and those with
    constant pain. Their results strongly suggest that MVD should be considered
    for a subset of patients with atypical TN.
    Patients were divided into two groups: those with brief, lancinating,
    episodic pain (Type 1 or typical), and those with constant, burning
    pain with episodic exacerbations (Type 2 or atypical); 135 patients
    underwent MVD, 67% of whom were classified as Type 1 and 33% of
    whom were Type 2. In the Type 2, atypical pain group, complete relief
    of the episodic component of the pain was demonstrated in 77%, and
    complete relief of constant pain was achieved in 70%. Significant pain
    relief was achieved in more than 80% of patients, regardless of their
    classification.
    This report demonstrates the importance of diagnostic precision in
    predicting outcome from neurosurgical interventions. In this series, all
    patients with Type 2 TN originally started out with Type 1 TN. Given
    the good results in this patient group, an initial typical presentation
    appears to be an important diagnostic criterion for success of MVD.
    Continued refinement of our ability to recognize facial pain syndromes
    as distinct entities will lead to further improvement in outcomes. Not
    all facial pain is due to TN!
    Jaimie M. Henderson
    Stanford, California

    The diagnosis of TN is a clinical diagnosis based on a careful history.
    There are no definitive tests to verify the diagnosis. The failure of
    MVD in the management of facial pain other than that from TN makes
    this clinical diagnosis extremely important for the neurosurgeon.
    Traditionally, neurosurgeons have reserved MVD for patients with the
    typical symptoms of TN neuralgia and have avoided MVD when the
    presentation is atypical. In the current publication, Sandell and Eide
    have analyzed the results of MVD in a series of 135 patients undergoing
    the procedure, one-third of whom underwent surgery for atypical
    TN. Interestingly and importantly, 70% of patients with atypical TN
    achieved complete pain relief, and 77% achieved significant pain relief.
    These results are quite comparable to the results attained in the group
    of patients with typical TN.
    It is extremely important that the reader note the definition of atypical
    TN used in this study. These are not patients with atypical facial
    pain or patients with trigeminal neuropathic pain. In the preoperative
    assessment of his patients, the senior author was quite careful to determine
    whether or not atypical pain had developed in the course of more
    typical TN. MVD was reserved exclusively for patients in whom an
    atypical TN developed in the course of more typical TN. Therefore,
    these data apply only to patients with TN who have developed atypical
    symptoms (constant facial pain of burning, aching, and throbbing
    character) after initially having typical TN. The results suggest that
    this group of patients may also benefit from MVD and should be considered
    for treatment.
    Daniel L. Barrow
    Atlanta, Georgia

    Sandell and Eide commented that the presence of constant pain creates
    concern over the presence of deafferentation pain. I am less
    convinced that this represents a major dilemma, as deafferentation pain
    generally results from the ablative procedure, whereas constant pain
    present before the ablation can easily be recognized as a component of
    the original syndrome. In the present study, only 10 patients presented
    with constant pain and a history of a previous ablative procedure.
    The present study and current classification schemes focus on constant
    versus episodic pain as the major indicator of “atypia.” However,
    patients may also present with pain outside the trigeminal distribution
    and psychological overlay. Thus, I tend to view tic as a continuum
    from classic (no psychological overlay, within the Vth nerve distribution,
    and purely episodic) to highly atypical. Indeed this continuum
    extends from atypical TN to atypical facial pain.
    Ultimately, the more atypical a case of TN is, the less apt I am to do
    MVD without radiological evidence of significant vascular compression.
    On the other hand, I am extremely hesitant to perform ablative
    procedures on patients with less typical symptoms. This bias comes
    from the fact that ablative approaches to constant neuropathic pain
    throughout the body tend to have poor durability and can cause deafferentation
    pain. Thus, my approach has been to proceed with neuromodulation
    approaches including peripheral nerve, ganglion, motor
    cortex, and deep brain stimulation in patients with predominantly
    constant pain (atypical TN) in whom I cannot find a vessel on imaging.
    If I can find a vessel, I will always perform an MVD before
    embarking on neuromodulation, because the former procedure has
    the potential for cure, whereas neuromodulatory approaches generally
    produce only partial relief. Moreover, the latter require indwelling
    devices with all of the associated morbidity. Finally, the durability of
    facial pain relief with neuromodulation is unclear. Put simply, whether
    or not MVD is as good for constant pain or episodic pain, I would still
    use it for atypical pain if imaging is suggestive of a vessel. Although
    the study by Sandell and Eide will not change my protocol, it provides
    encouraging data to support MVD in discussions with patients with
    Type 2 TN.
    The authors note that constant pain may occur de novo, but all of
    their patients with Type 1b/2 TN reported that the syndrome started
    with purely episodic pain (Type 1a). This feature may be an important
    clue to implicate a vascular etiology and explain why MVD is so successful
    in these patients. When discussing MVD with patients with
    Type 2 TN, it will be important not to quote these results to those who
    presented originally with a predominantly constant pain syndrome.
    Finally, the present study convincingly contradicts the popular notion
    that the constant pain component of TN syndromes derives from
    venous compression.
    Nicholas M. Boulis
    Atlanta, Georgia

    It is conventional wisdom that the paroxysmal component of TN
    pain is best relieved by MVD surgery. A common corollary of this
    postulate is that patients with significant constant pain as part of
    their facial pain syndrome do not fare as well with MVD. Some surgeons
    go as far as not to operate on such patients for fear that their
    atypical features imply a worse clinical outcome. In this article,
    Sandell and Eide challenge this conventional wisdom with their experience
    in treating patients with such pain. In this retrospective review
    of a series of 135 patients, they compared the results of patients with
    less than 50% constant pain with those whose constant pain is more
    than 50% of the total. Those patients with pure paroxysmal pain were
    also analyzed as part of this study. The group as a whole was treated
    in a similar fashion, by a single surgeon, at a single center. Follow-up
    ranged between 1 and 7 years. They found that the relief of both
    paroxysmal and constant pain occurs with high frequency after MVD
    and does not seem to depend on the degree of preoperative constant
    pain reported by the patient.
    The message of this article is that MVD should not be denied merely
    because of the presence or even degree of constant pain in the symptom
    complex. And although Sandell and Eide provide good information
    to support this message, it should be remembered that the data
    may be confounded by a number of factors. Given that this is a retrospective
    study, for example, it is quite likely that baseline patient characteristics
    in the three groups are not comparable. Moreover, the widely
    disparate follow-up period may yield comparisons between groups
    followed for different periods of time. Finally, it is important to remember
    that because entry into this study was not randomized or controlled,
    the number of patients in each group varied widely. It is difficult,
    therefore, to make definitive conclusions about the effect of
    constant pain on results after MVD.
    Despite the limitations inherent in a retrospective study, the authors
    here do a good job of examining the role of nonparoxysmal pain on the
    results of surgical treatment. Their data certainly show that constant
    atypical components of trigeminal neuralgia may not be such a poor
    prognostic factor after all.
    Oren Sagher
    Ann Arbor, Michigan

    Leave a reply →

Feedback about this page

Leave a reply

You must be logged in to post a comment.

Photostream